In August of 1914, the guns of war began to sound. In response to the Austrian declaration of war against Serbia, Russian forces mobilized and entered Austrian Galicia in an attempt to secure trans-Carpathian passes. In response to the failure of the Russian government to stand down, Germany declared war on not only Russia, but their French allies in an attempt to secure a decapitation strike before the latter could prepare. In response to this, prepared Russian forces entered Prussia and Prussian Poland, even as France and the United Kingdom moved into Belgium to secure that state's independence. As German force bogged down in Brussels, Russian forces pinned down German reinforcements to the rapidly-collapsing Austrian nation in Silesia and Slovakia, having secured Romanian support to the Serbian state with the promise of Hungarian Transylvania and a decisive demonstration of the Hungarian weakness at Presov, then brought their primary hammer down, aiming across the frozen Oder at the heart of Germany. At 13:00 GMT of January 30, 1915, Russian forces under the command of von Val and Ruzsky triumphantly entered Berlin, missing the Kaiser's departure to Essen by a matter of hours. The German government initially vowed to fight on, demonstrating the new nature of the industrial war as they pinned their hopes on the armies of Silesia, but it would be a mortal wound from which they would not easily recover as the Russian army took free reign in central Germany. The failure of the German armies at Oppelin and Katowice, combined with Russian cavalry ranging into Hamburg and main army groups approaching Hanover, finally compelled the German Kaiser to see reason, and on March 4, the Chancellor was instructed to seek an armistice. Bereft of aid, Austria was compelled to surrender three days later, and Bulgaria on March 11. For the cost of 1.6 million German casualties (both killed and wounded), 1.1 million Russians, almost half a million Austro-Hungarians, and another half-million from the Western Entente, honor had been preserved, and a new European order was to come.
...I'm feeling this mod might have the same "overpowered Russia" problem that seems to follow so many WW1 games.
Darkest Hour: The Grand Campaign mod