The Great Eastern War (French: ; Russian: ; Polish: ; German: ) was a major conflict in Eastern and Central Europe from 1937-40, in which the Republic of Russia, under the rule of the authoritain, pan-Slavic nationalist People's Party (known as the Narodniks) attacked neighboring states as part of its "Restoration Campaign" to retake early 19th century Russian borders and to construct a South Slavic ally state in the Balkans, as well as potentially seizing the Turkish Straits. The surprise offensive triggered defensive alliances between Saxony and Poland and resulted in the mobilization of much of Western Europe under French leadership, as well as the Turks fighting on their own front in the Balkans alongside their Rumanian protectorate.
After years of rising tensions, Russia's Narodnik forces were able to inspire uprisings in many South Slavic and Orthodox states and succeeded in pushing through Livonia and most of north-central Poland into eastern Prussia with rapid advancement, but were bogged down in Rumania well before reaching the Danube and were stuck at Lwow in Poland for three months. 1938 saw the forces strike a stalemate; after the Spring Offensive nearly reinvigorated the Russians and brought them to the gates of Dresden and Berlin, they settled into brutal trench warfare in western Saxony and were unable to pierce the Carpathian defenses of Danubia. The Carpathian Offensive of October 1938, the brainchild of Prince Sebastien Bonaparte, blew through Russian supply lines after the Russian defeat at Lutsk that November, and retook Warsaw and Krakow.
Despite efforts through early 1939 to find a ceasefire, particularly after Emperor Albert I of France died and his son __ replaced him and the Narodniks violently put down an attempted coup in the Bryansk Barracks Revolt, the new French government, egged on by its own vehemently nationalist and tyrannical elements, refused, as did the hardline Narodniks, and the campaigning in earnest resumed shortly thereafter with the Southern Offensive. Russia withdrew from Rumania after two years of stalemate near the Danube with Turkey; Turkey largely exited the war at this point after occupying Odessa and blockading Russian Black Sea ports, preventing supplies from entering Russia. The Southern Offensive succeeded in taking Kiev and the Donetsk Basin and the Kharkov area by years' end, and in the north the Entente was able to take Minsk and Smolensk, as well as advancing to Riga, thus threatening the Russian heartland for the first time. Late in 1940, Sebastien persuaded Sweden to join the conflict with promises of Karelian territory; the Swedish joined in the Winter War, opening up a new front near Petrograd in late winter, and Russia was forced to withdraw forces from restive Georgia and Armenia in order to solidify its position in the Caucasus in anticipation of a three pronged "Final Offensive" - Petrograd in the north, Moscow in the center, and through Rostov to Tsaritsyn in the south.
The 1940 operations nearly seized Petrograd with Swedish soldiers, and while the southern theater came bogged down in muddy conditions around Rostov, the March on Moscow and popular anger resulted in a mass revolt by the 8th Army, resulting in the evacuation of the Denikin government to Novgord in the east and Sebastien's triumphant march into Moscow. The Novgorod government would continue fighting in eastern European Russia through 1941, when it was finally put down in a bloody coup d'etat at the same time that the Provisional Duma, as the new regime in Moscow was called, was overthrown by a secretive military cadre that would eventually reconsolidate power throughout a war-weary Russia.
The Great Eastern War was a direct catalyst for the French Civil War; an assassination attempt in Moscow against the hugely popular Sebastien was traced back to Francois Baptiste, the State Minister in Paris. Escalations between Loyalist and Sebastienite forces, with many European regimes sympathetic to the Prince who had helped rescue much of the continent from the Russian onslaught, eventually spilled over into open conflict in France proper and across the continent. With many of the Russians he had just recently been fighting, Sebastien swept across the continent with loyal nations backing him against his brother and eventually seized power in Paris in October of 1943. For this reason, the Great Eastern War and French Civil War are often regarded as one continuous period of conflict in Europe.