Prelude: Alternate Result at the Battle of KosovoIn our timeline (OTL), the Ottoman Empire had won the Battle of Kosovo in 1389. In this timeline called Timeline Heliopolis, the Serbs had won the Battle of Kosovo instead of the Ottomans.
After the Turkish counterattack aimed at the Serb heavy armor that was charging at the Turkish wing command, the Serbian forces regrouped at the upper hill that overlooked the battlefield, and harassed the incoming Ottoman army. Repeated Serb counterattacks had led to the Ottoman forces retreating from Kosovo all the way into northern Greece.
With the Serb victory at Kosovo, they were now in a better position to counter the Hungarian invasion that was looming over the border. Eventually, the Kingdom of Hungary saw the strength that the Serbs had demonstrated over the Ottoman armies and resolved not to invade the north.
The Serbian EmpireWith their territory in the western Balkans secured, the Serbian Empire was given the opportunity to flourish. Having defended its southern territories from Ottoman rule (in what is modern-day Montenegro, Albania, Macedonia, and northern Greece), Serbia had become a regional and military power, and it would remain that way over the next few centuries.
With the Ottomans expelled from the western Balkans, Serbia was able to turn its attention elsewhere, and that it did. One of Serbia's biggest rivals was the Kingdom of Hungary, who had unified with the Kingdom of Croatia back in 1102. The two countries were locked in cold relations that over five long decades, since both were reluctant to start another Balkan War with the Ottomans right at their doorstep. However, as time drew on it became apparent that the Ottomans were not going to attack again anytime soon, and thus both Hungary and Serbia slowly prepared themselves for a great Balkan war.
In 1447, Hungary invaded and conquered the Kingdom of Bosnia, which had become a country within Serbia's sphere of influence. Serbia, recognizing the growing Hungarian dominance in the region as a threat, resolved to take action against their rival once and for all. Serbia launched an invasion of Hungary in 1448, under the pretext that they wished to liberate their Slavic brethren (the Croatians and Bosnians) from Hungarian rule. This triggered the Serbo-Hungarian War, which would last a bloody 26 years before it finally ended in 1473, when the Serbian forces captured Hungary's then-capital of Buda.
The Hungarian defeat finally secured Serbian dominance in the Balkan Peninsula. The King Matthias of Hungary was forced to abdicate the Croatian throne, and the Hungarians lost access to the Adriatic Sea. The Serbian Empire annexed Vojvodina. In the battle for dominance in the western Balkans, Serbia had triumphed. Hungary would need to look to establish dominance elsewhere.
Following the abdication of the Croatian throne by the Hungarian king, the Kingdom of Croatia was left in a weird state of limbo. Having no direct heir to the throne (other than the disgraced Hungarian royalty), many Croatian noblemen began to fight for the throne, which ignited several months of political infighting over the Croatian succession. This infighting only further damaged the kingdom, which had already seen its homeland destroyed in the Serbo-Hungarian War.In hopes of establishing a lasting foothold in the region, Stefan Uroš VI (the Serbian tsar) proposed that he should be new monarch of the kingdom, citing a very distant connection to the Croatian royal bloodline to claim his legitimacy to the throne. At first, the Croatian government was skeptical of these claims and vehemently opposed a union with Serbia, since many of the powerful aristocrats sought to claim the throne for themselves. However, through clever political scheming, Uroš was successfully able to maneuver his way around the Croatian nobility and announce himself as the heir to the Croatian throne, a move that was met with support from the peasantry and a sudden increase in Serbian military presence on Croatian soil. With support only growing for Stefan Uroš VI, it quickly became apparent that the nobles would not have a say in the matter; Uroš would be crowned whether they liked it or not.
Thus, in 1475, the Stefan Uroš VI was crowned the new king of Croatia. This put Serbia and Croatia into a personal union and soon added Croatia as the newest addition to the Serbian Empire. Bosnia would join the empire soon after to receive military protection from the Hungarians who had attacked them many years ago.
Rise and Fall of the Yugoslav Empire
However, despite their triumph over the Hungarians, leading the enlarged Serbian Empire quickly proved to be problematic. The mountainous geography of the Balkan peninsula made unification difficult, and the dominance of Roman Catholicism among the Croats conflicted strongly with Serbian Orthodoxy. Following numerous peasant revolts of the Croatia, the union between the Serbian Empire, the Kingdom of Croatia, and smaller Balkan states (Bosnia, Herzegovina, Dubrovnik, Macedonia, and Albania) would be reorganized in 1526, into what was known as the Yugoslav Empire. Both Croatia and Serbia remained in a personal union, but each retained a significant amount of autonomy, with the western capital in Zagreb and the eastern capital in Belgrade. However, despite this loose structure, the union was surprisingly stable and would last for another 250 years before its eventual disintegration.
Age of Exploration and Colonial AmbitionsColumbus' discovery of the Americas in 1492 had taken Europe by storm, triggering a new age of exploration and discovery. Nations from all over Europe were eager to explore the New World, and the western Balkans were no exception. This led directly to the Yugoslavian explorations of present day North America and much of South East Asia.
The acquisition of the first colony of Yugoslavia occurred after its role in the alternate Spanish-Yugoslav War in 1764, after the Seven Years War. The Kingdom of Spain, wrecked by its defeat in the Seven Years War after the British occupied Cuba and the Philippines, faced another threat. This time, Yugoslavia had challenged Spanish superiority at the naval Battle of the Mediterranean, which Spain narrowly won. Although the Yugoslav naval power was weak at that time, it eventually grew thanks to British support, who at first supported Yugoslavian ambitions after its contributions in the Seven Years War. The empire's colony however, was the Gibraltar colony which would eventually be under British control.
The two kingdoms remained allies for a few years, but this relationship quickly turned sour. As time drew on, Britain's naval superiority was threatened by the expansion of more Yugoslav fleets anchored in the port of Bar in the Adriatic. Before long, the alliance between the two nations finally came to a head, and the two empires saw one another as rivals on the world stage.
The Anglo-Balkan War of 1768
The fall of the Yugoslav Empire began in 1768. During this time, the Kingdom of Great Britain had become increasingly aggressive and sought to expand its interests to the Balkan Peninsula, hoping to gain free access to Africa via the Adriatic ports. And Hungary and Yugoslavia were in the way of these ambitions becoming a reality. Thus began the Anglo-Balkan War.
Britain's first victory in the Balkans was at the Battle of Podgorica, when the British army overran Yugoslav positions stationed in the city. Sensing opportunity to keep their Balkan rival under British thumbs, the Hungarians allied themselves with the British, and they too joined the war.
The war also drew in the Russian Empire, which was both looking for more warm water ports and anxious to get its revenge against the British for its loss in the Seven Years War. Seeking to help their Slavic brothers, the Russian forces allied with Yugoslavia, and invaded and defeated the Hungarian Kingdom on the outskirts of Budapest. British gains were rapid, occupying Nis, as well as other cities and towns. However, Britain's first defeat of the war was at the Battle of Belgrade. The battle in the Serbian capital was bloody and brutal, plus frequent harassment form native resistance groups operating in the city. Eventually, Belgrade was overrun by British forces.
Dissolution of the Yugoslav Empire
With one-half the empire occupied (including the main capital), it was not long before Croatia, too, submitted under British pressure. At the Treaty of Zagreb in 1769, the Yugoslav Empire was officially dissolved as the Serbian tsar was forced to abdicate the thrones of both Croatia and Serbia. The British Empire was victorious.
Aftermath of the Anglo-Balkan War
For the first time in almost three centuries, Serbia was occupied by a foreign power. The Anglo-Balkan War ended in a stunning British triumph, leaving Serbia and Croatia occupied in a humiliating defeat. A British sphere of influence formed around the Dalmatian and Albanian coast, and the two kingdoms were reorganized into a British-held territory known as the British Balkans, which consisted of the kingdoms of Croatia and Serbia under the British crown.
Russia once again lost the war to its possible rival, once again having been denied the chance for access to a warm water port.
Hungary, despite having been allies with Britain in the war, did not get the victory they had wanted. Despite having reclaimed Vojvodina, their homeland had been ravaged in the war against the Russians, and, in their weakened state, they too fell under the thumb of the British.
Now, Britain had control of both the Balkans and North America. Having defeated Spain, France and Serbia, the British Empire had risen among the rest as the dominant colonial power on the world stage.
The American Revolution
The opportunity for revenge occurred when the colonists in the 13 Colonies of British America rebelled against Britain in 1775. Serbia took advantage of this opportunity to resume its resistance against British occupation by assassinating a British Deputy Assistant to the military governor at the time.
Struggling for independence was the vocal point of the British-occupied territories and colonies' goal of driving its imperial masters out of its own territory. During the American Revolution, particularly in the late stages of the conflict, Serbia (along with France, Spain, and the Netherlands) sent volunteers to aid the revolutionaries in the fight the British.
In the meantime, Russia, led by Catherine the Great, was eager to spread its influence across the Balkans to acquire access to warm water ports and took this opportunity to support the Revolution alongside its South Slav brothers. Britain, focused on fighting the Americans and the French, largely ignored the Russians, neglecting its interests in the Balkans. Subsequently, Serbia was liberated by the incoming Russian Army in 1780 (breaking free from the British Balkans) but the armies reached a standstill at the Serbo-Croatian border, in which British overseas forces had remained to maintain occupation of the British protectorate.
Liberation of Serbia
After the Treaty of Paris of 1783, Serbia and Russia negotiated the sovereignty of the new Serbian monarch and the Serbian borders to the British Balkans, to which the weakened British Empire agreed to recognize (albeit reluctantly). Croatia, however, remained under British occupation, and would continue to be part of the British Balkans until the region was conquered by Napoleon Bonaparte in 1805.
The Napoleonic Age
Serbia pretty much stayed out of the conflict in the early stages of the Napoleonic Wars. However, with the French Empire's occupation of Croatia and annexation of what was known as the "Illyrian Provinces", Serbia almost went to war with France. It wasn't until the French invasion of Spain that Serbia started to invade Spanish-held Philippines. With Spain busy fighting off French occupation, Serbia quickly drove off the Spanish at the Battle of Vigan. From this point, Napoleon considered the Serbs to be allies and decided they did not fall within his interests (which he later turned toward Russia in 1812).
Toward the end stages of the Napoleonic Wars, Serbia finally turned against France and joined the War of the Sixth Coalition. This was done in an opportunity to restore its alliance with Russia, but also to try and rekindle relations with Britain and Austria, who were both smarting from the loss of the control of the Balkans.
Congress of Vienna
At the Congress of Vienna, Serbia sought to secure their territory by annexing parts of eastern Bosnia and acquiring the Philippines from Spain and Indochina from France (which had been established earlier in this timeline under Napoleon). At this time, Serbia was considered to be a junior member of the Big Five Powers (i.e. Prussia, Austria, Russia, France and UK), as a developing country and Russian ally, so they were given a significant voice at the conference.
One of Serbia's main goals at the conference to ensure the reestablishment of Croatia as a Serbian ally independent from either British, French or Austrian rule. Serbia flirted with the idea of reunification with Croatia, but this idea was struck down by Austrian foreign minister Klemons von Metternich, who hoped that an independent Croatian kingdom would someday marry into the Habsburg crown of Austria.
In the end, Croatia was established as an independent buffer-state between the Serbs and Austrians, much to the dismay of the British.
Serbia in the Early 19th Century
The Serbian Colonial EmpireAfter Serbia's acquisition of the Philippines in 1815, the Serbs then proceeded to control Indochina, which consisted of present day Vietnam, Laos and Cambodia. However, Serbia got into a war in Southeast Asia when the Dutch tried to invade the Philippines a decade later, leading to the Serbo-Dutch War of 1825. After gaining a swift naval advantage, Serbia was able to lead a counterattack on the western isles of the Dutch East Indies, invading from Serbian Indochina. Soon the Dutch were forced to withdraw from the Philippines to defend the invasion, and after a while the two countries signed the Serbo-Dutch Treaty in 1826 to settle any remaining territorial disputes. In the treaty, Serbia acquired the several major islands from the Dutch, including Java, Sumatra, and the western part of Borneo.
Serbia consolidated its control of its colonies further by expanding its economic development, particularly in the islands of Sumatra and Java in present-day Indonesia, and Manila in the Philippines.
With Croatia free from foreign control, it too started to seek colonies for its growing stable economy. However, Croatian ambitions clashed with Serbian ambitions, and even came close to war in 1828. Luckily, both nations were too weary from the other wars that they had to waged in order to survive and tended to view one another as allies despite their conflicting interests, and the issue was resolved peacefully.
Serbian Involvement in the American Civil War
When the American Civil War erupted in 1861, Serbia and Croatia first stayed neutral in the early stages. The reason for that was because both nations were threatened by Britain and France to stay out of the conflict, or face consequences. The British and French, while being anti-slavery, secretly supported the Confederates, hoping to weaken the growing influence of the United States on the world stage.
However, the threat didn't keep Serbia from contributing its forces to primarily Union forces, as Alexander II of Russia had already contributed forces to the Union and Serbia was persuaded to join. Croatia didn't contribute any forces at all, instead it kept alert for any possible future conflict with Britain.
Unfortunately, unlike in OTL, the aftermath of the American Civil War ended with a Confederate victory, which proved disastrous for the Serbian Kingdom. Britain was poised to invade Serbia once again, only this time at its colonies.
The Second Anglo-Balkan War
The attack on Manila harbor was known to Serbian authorities, who were planning this conflict after the disastrous event during the American Civil War. In 1866, Britain invaded the Philippines once again. The first invasion was almost a hundred years ago. This time, Serbia went fully prepared for the combat. The war would have gone longer had not the Russian Empire intervened, as they too had been involved in support for the Union alongside Serbia to begin with.
When the war was over, Britain was forced to pay reparations to Serbia and Russia in goods as a result of its defeat. The timely intervention of Russia at the Battle of the Mekong River had proved to the British that it needed a partner quickly.
World War One
New Empires Emerge
In 1867, during the Anglo-Balkan War, the Austrian Empire had been reformed under pressure from the Kingdom of Hungary, which established the Austro-Hungarian Empire. Germany had unified in 1871 as a result of its first victory in combat resulted in the Franco-Prussian War, in which France lost. Italy also emerged back in 1866, and were planning an alliance with Germany and Austria-Hungary.
German fears of a powerful Serbia were already realized when it witnessed its industrial power in its Southeast Asian colonies during the peak of its economic boom in 1887. Austria-Hungary also feared Serbian domination of the Balkans when Croatia refused to accept a proposal for a three way monarchy between Austria, Croatia and Hungary. Croatia at this time had annexed several islands along the Dalmatian coast, and Serbia campaigned to recapture the Hungarian region of Vojvodina.
Japan also became an emerging power back in 1877, after the US helped modernize its army. Serbia, wanting to also modernize its army, also asked the US for help. As a result, a US-Serbia treaty had came into effect. Russia also was aware of what was happening in the Balkans, and signed a treaty with Serbia.
Serbia and Croatia planned to be neutral in any case a future conflict broke out, but with Britain planning on joining the Triple Alliance as well as CSA, they did not have much of a choice. The Second Union-Confederate War broke out in 1890, with the CSA winning it once again. The Russo-Japanese War of 1904-1905 was contested over the control of Korea and Manchuria, in which Japan won. However, Japan also lost its first modern war during the Serbo-Japanese War as a sign of retaliation for Serbia's support for Russia in the Russo-Japanese War. The Serbo-Japanese War was fought over Serbia's Southeast Asian colonies. However, this war did not last long, as the growing presence of great powers such as Germany and Britain made both sides worried, and a peace treaty was signed in 1906 (declaring a stalemate), which allowed Serbia to keep its colonies.
The planned alliance between Britain, Germany, Austria-Hungary, the Ottoman Empire, and Japan couldn't be realized because Britain was more concerned about France and the Confederate States being potential enemies if it joined with Germany. Thus, Britain aimed to bring its potential enemies into an alliance to avoid war with them. The United States also couldn't join Germany's side for fear of losing support of its Slavic allies, and they certainly were not going to join on the side of the British after their obvious support of the CSA. So, a three-way alliance was formed with Britain, France and the Confederate States being the Triple Entente, and with Germany, Austria-Hungary, and Ottoman Empire being the Triple Alliance. Serbia, Italy and Russia, all refusing to join either side of the oncoming conflict, signed a defensive pact in Belgrade in April of 1904 (Italy joined due to fear of Austria-Hungary). This formed an alliance known as the Belgrade Combine, later to be known as the Combine Powers. Croatia, being an ally of both Serbia and Russia, joined only two months later.
During the 1900's, former Ottoman Empire territories had already broken away with support of Serbia and Russia. As a result, Bulgaria became independent in 1908 and joined the Combine Powers for support in fighting the Ottomans. Additionally, since the Serbo-Japanese War had ended several years earlier, Japan also joined the pact in an effort to rebuild their relationship with Russia and Serbia, though it was more for strategic reasons than the desire to form an alliance.
The Great War
Serbia had covertly planned the assassination of Franz Ferdinand in Sarajevo while on a state visit to Croatia, feeling threatened by the new empire's ambitions for a union with Serbia's close neighbor. Like in our timeline, Austria-Hungary blamed Serbia for the assassination, and sent an ultimatum. When Serbia refused to accept the ultimatum, Austria-Hungary declared war on Serbia. The Russian Empire then mobilized its troops and declared war on the Austro-Hungarian Empire. Germany did the same thing and declared war on Russia. Japan also mobilized and declared war on Germany, Austria-Hungary, and the Ottoman Empire. At first, Britain and France would sit this conflict out, but the desire for another great war against the United States, Serbia, Russia and Germany proved too much to handle, and they soon declared war on both the Belgrade Combine and the Triple Alliance (Central Powers).
The first conflict started with the Austrian bombardment of Belgrade in September 1914. However, the siege had to be broken off because of Russian offensives poised to attack Transylvania. Germany then proceeded to attack France through Belgium, and Britain sent reinforcements.
The Confederate States invaded the United States in early October, hoping to defeat their northern neighbor once again with support from their Triple Entente allies. In response, American president Theodore Roosevelt declared war on the Triple Alliance and sent support for both the Triple Alliance and the Combine, but joining neither side.
Germany signed a pact with the Qing Empire of China, but revolutions in which the Kuomintang was first born made it impossible for the Kaiser to send aid to its Asian ally. Japan then proceeded to attack German held territories in China at the Battle of Tsingtao in November 1914.
In 1915, Bulgaria shocked everyone when they switched sides and defected to the Central Powers, hoping to claim Macedonia (which was full of ethnic Bulgarians) from their ally Serbia. The result was a massive invasion the culminated into the Battle of Cer in 1915 (primarily against the Austrians), in which Serbia won but suffered huge losses. Bulgarian, Austrian, German and British mobilization had a huge effect on Serbia when they were defeated in October 1915, with Belgrade occupied. Serbia almost collapsed until Russian reinforcements prompted the opposing sides to fight the huge but ill equipped Russian army.
Croatia then staged an invasion of the Austrian half of the Austro-Hungarian Empire when the Austro-Hungarian army suffered a defeat by Russia in the Battle of the Masurian Lakes. However, Russian weaknesses that were facing its army proved to be futile when Germany scored major victories over Russia. In the Balkans, Croatia then suffered a defeat by the Austrian troops.
Britain then also invaded Croatia and Serbia from its overseas territory in Egypt through the Adriatic Sea. When Croatia and Serbia were on the verge of collapse, and Russia on the defensive, Japan sent troops to help with the Balkan Front. This move brought into conflict between Japan and the Ottoman Empire with the Japanese Navy defeating the Turkish Navy at the naval Battle of the Persian Gulf.
Japanese troops also scored victories against the Austro-Hungarian armies in the Serbo-Japanese offensive at the Battle of Kosovo in March of 1916.
1917 was the year of huge losses. After a crushing defeat at Sarajevo, Croatia finally capitulated under Austro-Hungarian pressure and fell to the Central Powers. To make matters worse, it was becoming increasingly difficult for the Russian Army to defend their homeland from the German invasion. The losses on the Eastern Front were staggering and left mass dissatisfaction among the Russian populace. Just like in OTL, Lenin and the Bolsheviks gained support and the tsar was soon forced to abdicate. As the country became wrapped up in the Russian Revolution, it was unable to continue to fight and was eventually forced to sign an armistice with Germany in December.
The losses of Russia and Croatia were a devastating blow to the war effort of the Combine Powers, but it was also a cause for concern among the Triple Entente, who were fighting Germany in France. With more German troops allocated to the Western Front, Britain and France became worried and quickly wrote up an armistice with the Combine countries. The Combine accepted just so long that ending the fighting on Allied terms would not be perceived as a surrender. The Allies and Combine Powers were in agreement, and Britain withdrew its troops from the Balkan Front so they could all focus their energies against the Central Powers. With their forces freed up, the Serbian forces launch a full offensive in an attempt to reclaim Belgrade from Austrian occupation. The battle was a success, and the Serbian capital was reclaimed. From Belgrade, the remaining Combine Powers planned a two-pronged attack to seize Vojvodina and liberate Croatia from occupation. The advance reached a standstill at Novi Sad and Mostar, and the war raged on from the trenches.
On the American Front, trench warfare between the USA and CSA continued to rage at a harsh stalemate. However, the armistice signed between the Allied Powers and Belgrade Combine motivated the US to declare war on Germany, as they wanted to be on the winning side.
Germany, fearing the sudden coalition that had formed against them between the Allies, Combine, and United States, launched an offensive of their own at the Second Battle of the Marne in July of 1918, hoping to claim Paris before it was too late. The attack failed, and German lines began to collapse under Allied pressure.
China was the first to capitulate to the Japanese military in October of 1918, exhausted by the war effort and unable to receive adequate support from their German allies. They were soon followed by the Ottomans, who collapsed later that month under British pressure. It wasn't long before Germany and Austria-Hungary were forced to sign an armistice too, which they did in November of 1918, on the eleventh hour of the eleventh day of the eleventh month of the fourth year of the war. This event would be remembered as Armistice Day in Europe.
With the Germans defeated, the Allies focused looked to the only front left on the war: the American Front, where the Americans had finally built up a clear advantage over the Confederates, mostly due to slave revolts that had begun within the Deep South. Due to the weariness of Allied forces, the British and French were unable to help their ally and urged them to surrender while their homeland was still mostly intact. The Confederates, initially unwilling to accept defeat at the hands of their northern rival, refused, but eventually gave into pressure from the invading American forces. This war continued until December of 1918, the CSA finally surrendered and signed an armistice with the Americans.
Aftermath of the War
In January of 1919, the Paris Peace Conference was convened between the leaders of the Allied Powers and the United States to discuss terms for the end of the war. One idea to create a lasting peace was put forward by President Woodrow Wilson of the CSA, who, despite having lost on his front of the war, suggested the establishment of an organization to maintain international law and world peace. This idea was opposed by the United States, but the British and French adopted the idea anyway, establishing the League of Nations in 1920 (an organization the USA would opt out of).
Under Allied terms, the Ottoman Empire was carved up into British and French colonies, and Austria-Hungary was split among ethnic borders. Germany was forced to accept guilt for the war in the Treaty of Versailles, where they had to give up their oversea colonies to the Allies, lost territory, and had to pay a massive amount of war reparations that would cripple the German economy in the years of the Weimar Republic.
China, although an ally of Germany, was never an official member of the Central Powers and had signed a separate peace treaty with Japan back in February.
The Belgrade Combine wasn't as punished by the war as the Central Powers were, but were still forced to pay reparations to the Allies. Bulgaria, being on the Central Powers, had been unable to claim Macedonia, so that remained a Serbian-held territory. However, Serbia was forced to give up their island colonies to Britain and Serbian Indochina to France, which marked the end of the Serbian colonial empire overseas. The Allies did let them have a share of reparations received from Germany, and when Austria-Hungary was carved up to allow Serbia to annex Vojvodina. Despite this, the loss of the Serbian colonial empire stung the Serbian population like an open wound, and left them incredibly bitter toward the British.
Among the other Combine countries, Croatia acquired Istria, and Italy gained Tyrol, Trieste, and Trentino. Slovenia, on the other hand, remained part of Austria and was given to neither. Also, similar to Germany, Croatia became a republic due to dissatisfaction with the king's policies and the destruction the country had suffered at the hands of the Austrians.
Despite territorial gains, all had to pay reparations to the Allied Powers. The treaty that created the Belgrade Combine was also forcibly dissolved, as the Allies saw it as a threat to the peace in Europe.
Of the Combine countries, by far the most bitter about the loss were Japan. The Japanese had been forced to give up the land it had occupied in China to the British and French, and lost Korea, which became a British protectorate. To the Japanese, this was unacceptable, as they were the ones who had won that land in the first place. They accused the Allies of taking advantage of the deal they had drawn up to ensure the defeat of the Germans. Such a humiliation would be remembered by Japan, and the two nations would butt heads repeatedly throughout the Interwar Period as Japan sought to reclaim their empire.
The situation in the USA was very different. Despite being an adversary of the British and French, the US had eventually come out victorious on their home front against the hated Confederates. Furthermore, the industrial nature of the American economy had been jump-started due to the war, and America would soon see an economic boom that would help them rebuild the cities that had been destroyed during the war with the Confederacy. All this revitalized the American spirit, and during the rebuilding of American cities this gave way to an era of cultural and economic revival that would later be known as the Roaring Twenties.
The CSA was not quite as happy as their northern counterpart. Since they had refused to surrender until it was too late, the Confederate homeland had been ravaged by Union forces and slave revolts, which made reconstruction difficult. Their defeat in the war also marked the abolition of the Southern practice of slavery, which in this timeline remained a vital part of the agricultural Southern economy well into the early 20th century. This led to immense hyperinflation and an economic crash during the Interwar Period, and the CSA would be hit harder than any other nation during the Great Depression in the 1930s, especially during the Dust Bowl, which destroyed agriculture in the South. The CSA blamed the USA for their losses, as well as the British and French, who they believed had forsaken their alliance to appeal to the Americans.
The Interwar Period
Communism, Fascism, and Pan-Slavism
Meanwhile, the Russian Revolution was continuing in full effect. Serbia, having been a strong ally of Russia in decades past, supported the White Army (as did many other European powers). This, however, was not enough to stop the enormous discontent in the Russian populace, and it wasn't long before the Bolsheviks crushed all opposition and Vladimir Lenin became the leader of the world's first communist state. Similar uprisings would happen in other states of the former Russian Empire, and in 1922 they would come together and form the Union of Soviet Socialist Republics.
In the wake of World War One, many countries had seen their homelands destroyed. Food was scarce, and economies had fallen apart over the course of the prolonged conflict. The countries of Europe began to turn to radical ideologies to restore themselves economically and militarily, and with the establishment of the USSR under Vladimir Lenin, many began to turn to communism.
Throughout the 1920s, a young Croatian socialist known as Josip Broz Tito, who was founder of the Croatian Communist Party, began to become well-known throughout the Balkans. As a member of the Croatian military whose division had been forced to flee to Russia for assistance, Tito had experienced the early effects of the Russian Revolution and became a stark advocate for workers throughout Europe. Not only that, but Tito began to call for a closer relationship between Croatia, Serbia, and Bulgaria, possibly to the extend of the reunification of "Old Yugoslavia" (which had not existed in over 250 years). Theoretically, the country would be very influential and strong with its strategic position along the Adriatic to the Black Sea, and would be strong enough not be pushed around by foreign powers any longer (namely Britain and Germany).
The idea of a socialist federation among the Balkan Slavs was an idea that became somewhat popular Croatia, and the Communist Party gained support in the Croatian Republic. The idea was especially popular among the Croatian Serbs, who, since the dissolution of the Yugoslav Empire, had longed for reunification with their motherland of Serbia. The idea gained some traction in Serbia and Bulgaria too, who are experiencing poverty as a result of the war and were sick and tired of being pushed around by the British for centuries. However, the idea of a federation is something that sparked an outrage for King Alexander II of Serbia (Alexander I of Yugoslavia in our timeline), who viewed the idea of a hypothetical creation of a communist state that included Serbia as treason against the Serbian monarchy. As communist ideas spread throughout the Balkans, the Serbian government banned the Communist Party in September of 1925 and cracked down on the rights of lower class workers. The Bulgarian tsar had similar worries, and they too banned communism later that month.
One threat that worried the Balkan nations was Italian dictator Benito Mussolini (leader of the Italian Fascist Party), who had taken power in 1922. Mussolini had become increasingly aggressive toward Croatia in particular when they put claims on Croatian territory such as Dalmatia and Istria.
The birth of fascism also led to the rise of the Croatian Ustashe (founded by Ante Pavelić in 1929), who were unhappy with the socialist direction the Croatian Republic was headed as well as the many Serbs who supported the movement. The Ustashe committed many atrocities and acts of terrorism against the Croatian Serbs. This horrified Serbia, who urged the Croatian government to hunt down the fascists and have them tried and executed for their crimes. Croatia agreed to hunt down members of the terror group, but the underground movement remained elusive. Relations between Serbia and Croatia would soon deteriorate because of this.
The Great Depression
Without the wealth and resources of its Southeast Asian colonies and the war reparations imposed by Britain, the Serbian economy suffered greatly. To make matters worse, the Great Depression hit Serbia in November of 1929, and as a result poverty ran rampant. Serbian workers began to question whether the king actually cared about his people, and if Serbia should continue to be a monarchy in the future. The country was quickly divided between extreme right- and left-wing groups, which gave rise to Serbian fascists and communists who rose up in protest of the monarchy. As divisions in the Serbian kingdom grew, King Alexander began to crack down on these movements to maintain stability, especially against communists, but with every new anti-communist law the more support they gained.
Tensions exploded out of control in October of 1934, when King Alexander II was assassinated by a Bulgarian nationalist while on a state visit to Marseilles, France. The death of the king threw the country into chaos, and in November a socialist coup declared the Republic of Serbia. The Serbian Army rejected the new government and moved to restore the monarchy under Alexander's son, Peter II. In December, the Monarchists attacked Bulgarian minorities living in the Macedonian region, many of whom supported communism and the idea of unification with Bulgaria. And thus, the Serbian Civil War began.
The Serbian Civil War
Like the Spanish Civil War in OTL, the fascist governments of Italy and Germany sent support to radical Serbian fringe groups to crush the Republicans. Under the influence of their allies, the Serbian radicals adopted a fascistic philosophy, stating that the Republicans were communists who would lead Serbia to ruin, and the Monarchists were idiots who were stuck in the past that had led to Serbian defeats prior. Many Radicals, led by Milan Nedić, blamed the Macedonians and Greeks living in the South for Serbia's military defeats, saying they had made Serbia weak as a nation since its very inception. They also advocated for the idea of an ethnically-pure Greater Serbia, which would encompass a large portion of what was currently Croatia.
The Monarchists fought both the Radicals and the Republicans, hoping to reinstate the monarchy. They too blamed ethnic minorities, but for a different reason. They saw the minorities as disloyal to the king, which had led to Serbia's many failures against the British. At the head of the Serbian Army was Draža Mihailović, who formed the Chetnik Detachment of the Serbian Army in 1935 and aimed for the extermination of ethnic minorities in southern Serbia, which included ethnic Albanians and Slavic/Greek Macedonians.
Republican Serbia's main ally was the Croatian and Spanish Republics, who supported the new government's socialist policies. The Tsardom of Bulgaria, though a monarchy, was also supportive of the Republicans, as they did not condone the atrocities committed against Bulgarians living on Serbian soil by the Chetnik Monarchists. France was also a reluctant ally to Republican Serbia in the conflict, as they were afraid of the growing influence of Nazi Germany and Fascist Italy in Eastern Europe.
Despite their best efforts, the fledgling republic did not stand a chance against the overwhelming force of the fascist movements. In January of 1936, the republic was overthrown and Nedić appointed himself Prime Minister. King Peter II was reinstated to appeal to the aggressive Chetnik movement, but the monarchy's position was only in name, and no longer held any real power. Both Monarchists and Republicans had to go into hiding or else they would be purged by the new regime. Nedić had successfully solidified all power around himself as a dictator, and under him Serbia fell under fascism.
The New Serbian Empire
After the Serbian Civil War ended, the new Serbian government proceeded to seek an alliance with Italy and Germany, since Nedić recognized the threat the other fascists would pose to Serbia should a war break out. Thus, he decided the best option to avoid conflict with Germany was to stay on good terms, and that he did.
Serbia also worked to rebuild their old alliance with Japan, who had recently gone to war against Britain and China to expand into Korea and Manchuria (now Manchukuo) and conquer Britain's colonies in Southeast Asia.
When the Spanish Civil War broke out in July of 1936, Serbia supported the Nationalists (led by Francisco Franco). The war was won by the Nationalists in 1939, and Spain, too, fell under fascism.
Despite the anti-British sentiment shared among the Serbian populace, many were unhappy with the new Serbian government's friendly behavior toward Nazi Germany. To many, an alliance between Serbia and a country built on an ideology of hatred toward the Slavs was unthinkable, even a betrayal of everything Serbia was supposed to be. They were also baffled toward the propaganda that suddenly condemned Croatians, Bulgarians, and Russians, whom they had been allies with for the past few centuries. As such, many riots took place within Belgrade, but all were put down by the iron fist of Nedić.
The Road to WWII
In 1938, following the anschluss of Austria, many Eastern European countries became worried about the growing fascist presence in Europe. In an attempt to counter the growing fascist threat, the leaders of Croatia, Bulgaria, Hungary, Poland, and Czechoslovakia decided to meet and discuss a treaty for a defensive pact. The Budapest Agreement was signed in June of 1938, and put into place the Intermarium Defensive Pact, which guaranteed the assistance to each country from the rest in case of an invasion.
In September later that year, the Munich Agreement was signed by British Prime Minister Neville Chamberlain and Adolf Hitler, allowing the annexation of the Czechoslovakian territory of the Sudetenland. The agreement outraged the Intermarium nations, as they saw Britain's appeasement of Germany as a betrayal to the integrity of the Czechoslovak state.