Italo-Austrian War (Loyal Italy)

Causes

 * Many border tensions between Italy and Austria-Hungary, including the Austrian Littoral, Trent and Tyrol.
 * Conflicts in the Balkans over the border between Italian-occupied and Austrian-occupied Serbia.
 * Conflicts over control of Montenegro
 * Assumed dissolution of Central Powers following the German Revolution
 * Ethnic tensions in Austria-Hungary, which convinced Italy of eventual collapse of Austria-Hungary.

Basis
On June 11, 1923, Italy invaded Austria-Hungary, beginning a campaign to gain control of the city of Trent. Austria-Hungary slowly began to mobilize and send troops, mainly via railway to Trento. The invading Italians were split into two groups, one of which would invade from the East, while the other would invade from the south.

Army Group South
The southern group, headed by Pietro Frugoni, hoped to stick to the eastern bank of the Adige River, all the way up to Trentino, so that travel could be through small towns in valleys instead of mountains. The Austro-Hungarian Empire had been mainly militias trying to assault and cripple the Italian Army through guerilla warfare and artillery assault from mountains. This succeeded, and when the first major battle occurred at Rovereto, the Italians were forced to retreat and suffer some casualties. Frugoni then lead his army across the Adige, and decided to avoid the river, where they would be an easy target and have a tactical disadvantage, choosing to go to the mountains. With winter setting in, he decided to take over Riva del Garda, and use it as a base for an operation to rejuvinate all troops while simultaneously luring the enemy troops to attack the well-guarded city. After capturing the city in late November, his army wouldn't move until January 21st, one week after the Battle of Riva del Garda, in which Austro-Hungarian troops launched an unsuccessful and costly assault on the city only to be defeated by the Italians there. The group went north from there, and then crossed the Adige in March from thenorth of Trento. They then assaulted Trento from its unprotected north, taking the city.

Army Group East
This group was led by Florenzio Aliprindi. At the Battle of Levico Terme, the group suffered a major loss, including many casualties, though there were also large casualties for the Austro-Hungarians. The group retreated east to Borgo Valsugana, where they received reinforcements and Aliprindi was replaced with Luigi Cadorna, the main military officer of Italy. Meanwhile, the Austro-Hungarian Army, led by Alfred Jansa, was heading South to launch a counterattack of Italy. Army group east was ordered to chase the invaders, and leave their objective of reaching Trento. Through the winter, both armies accumulated severe loss in morale and minor casualties due to starvation, altitude, and hypothermia. However, the Italian army caught up to the Austrian army in early January near Asiago. The result was a major battle which large casualties on both sides (slightly larger for the Italians), which essentially forced an Austrian retreat.

Austro-Hungarian Invasion
Vincenzo Garioni was given control of the Italian army in the Eastern Campaign, against Arthur Arz von Straussenburg. Straussenburg began the front with an invasion of Italy in February of 1924, as Austria-Hungary hoped that if they could get to Venice or Padua, Italy would request a White Peace. The Italian forces gathered and first had a major battle when they attempted to stop the fall of Udine, but this failed, and they were forced to retreat. In the reatreat, they decided to have most of the troops cross over the Piave River, while others try to funnel the Austro-Hungarians to the right place on the river and wear down their forces. When the Austro-Hungarians arrived at San Dona di Piave, they enterred the city, hoping to take it and cross the river. They took it on March 19th, but on March 22nd, they attempted to cross, causing the massive Battle of Piave, the largest and deadliest of the war. They were not expecting a large Italian presence awaiting them on the other side of the river, and were assaulted by artillery fire, bombings from airplanes, gunfire, and grenades. Of the 45,000 Austrian troops, only 9,000 made it across, where they were met by a strong force. Austria-Hungary suffered about 11,000 casualties, and they retreated by the end of the day. It would cause a counterattack which would continue for the rest of the war.

Lucinico and Gorizia
Italy began a massive counterattack, regaining all the way back to the Torre River. Garioni, seeing the success in the river strategy, feared a similar strategy would take place at the Isonzo River. That is exactly what occurred, and Austria-Hungary prepared at the Eastern banks of the Isonzo River, mainly near Gorizia. The Austro-Hungarians also sent a force to funnel the Italians into the trap, mirroring the strategy used against them. However, the Austro-Hungarian army was weaker following severe casualties, and at Lucinico, the Italians decide to fight a full battle against the group of th Austro-Hungarians to their south. What results is a victory for the Italians, and they take prisoners from that southern group of soldiers. The Italians cross the Isonzo to the south of Gorizia, and go around Gorizia to attack from behind, while leaving some troops at the other side of the river to pick off the Austro-Hungarians. They then attacked from the East of the city, and as some units attempted to cross back over the river, they were stopped by similar grenade throwing and aerial bombing. Some soldiers surrendered, while the majority of the army was pushed northwards, where they would be pushed along until Klagenfurt.

Great Push
The Italian army now had a great advantage in numbers over the Austro-Hungarian army. The Italians, though they had suffered some casualties, had manage to cripple and damage the Austro-Hungarian army to a large extent. Italy also soon received reinforcements from the Northern Front of the war, as that part was secure and the Austro-Hungarians had also switched much of their army in the Northern Front to stop the Italian invasion of Slovenia. The next goal for the Italians was to secure the Sava River, which would require taking the city of Laibach, as it was known in Austria-Hungary. Meanwhile, Italy easy seized control of Trieste, as Laibach was the larger focus. The Austro-Hungarian army resorted to mainly guerilla warfare, scorched earth, and general attrition tactics to hopefully stop the Italian army, but the Italians made it through the mountains and reached Laibach. There, they were met by a small Austro-Hungarian force which used guerilla warfare to try to fight off the Italian army. It did, in fact, manage to cause great casualties and decrease in supplies for its size, but it was unable to defeat the Italian army, and the city surrendered in August. A major push was called for so that the war could be over before winter and the troops would not need to fight in the mountains in the cold. The push was a success, and in the couse of one month, the Italian army pushed 40 miles northwards. By the end of September, they were just 10 miles away. They then crossed the Drava in early October, and on October 5th, they besieged Klagenfurt. The city fell on November 4, and on November 6, Austria-Hungary called for a negotiated peace with Italy by having a conference in Innsbruck.

Montenegro Campaign
Aliprindi was switched after losing at Levico Terme to head the campaign in Montenegro. The force tasked with capturing Montenegro consisted of about equal parts of Italians, Albanians, and Macedonians. The campaign proved to be pretty easy despite a somewhat small force by the Italians, as the Austro-Hungarians were more concerned with damaging the Italian Army than with saving Montenegro. Austria-Hungary, therefore, did not send its own troops, and instead let local militias fight the war. Serbia would form a large army which greatly outnumbered the Italians, but they were engaging more in training for a rebellion against Austria-Hungary than helping Austria-Hungary, and were often being counterproductive to the defense of Montenegro. As a result, the Montenegro Campaign was a success, and there was only one battle lost by Italy, which was at Herceg Novi, which would allow Austria-Hungary to keep its claim on the city.

Battle of the Adriatic
There were several minor naval skirmishes in the Adriatic Sea. The largest such battle, the Battle of Vis, was a major naval battle which had two major effects. First, it cemented naval supremacy for Italy, and allowed a blockade of Dalmatia, including future victorious battles at the harbors of Split and Ragusa. Second, it was the first success of bombing boats using planes, a tactic which allowed Italy to sink four Austro-Hungarian ships.

Bombing
Italy, trying to experiment with their air force, conducted bombings of cities throughout the war, with many different tactics. They famously bombed Pula using chlorine gas, which killed about a third of the population of the city and would be used again on the Austro-Hungarian controlled Serbian city of Nis. They also used conventional bombing on the cities of Split, Podgorica, Laibach, Klagenfurt, Zadar, and Trieste, as well as the use of tactical bombing in battles. Austria-Hungary had a smaller air force, but it did conduct bombings on Venice, Padua, and Udine, and causing lots of deaths and destruction in Venice by sinking parts, and in Padua by also dropping gas. The main goal in the bombings for Italy was to get Austria-Hungary to concede defeat, but for Austria-Hungary they wanted to wear out Italy so that they would stop fighting.

Treaty of Innsbruck
These were the terms of the Treaty of Innsbruck:
 * All land south of the Drava River, up until the OTL eastern border of Slovenia, would go to Italy.
 * Italy's northern border would be set to its modern OTL border
 * OTL Montenegro, except for Herceg Novi, would be given to Italy
 * The Austrian Littoral, including Trieste, would be given to Italy.
 * Ragusa and the nearby coast would be given to Italy.
 * Italy would give a small part of its land in Serbia to Austria-Hungary.
 * Both governments agreed to recognize the new German Republic.