Darkest Hour: A Hearts of Iron Game with Kaiserreich v1.5 mod.
Started playing as Hungary, which in the beginning is part of Austro-Hungarian Empire, basically a puppet under Austrian rule. Through event chain I started a civil war and won the Austrians in war that dragged on for 2 years and managed to secure independence.
During this time, situation on the Balkans was pretty hot; Serbia (who had conquered Bosnia and Croatia from me and Austria during our war), Romania, and Greece were planning a war against Bulgaria, who had conquered some of their territories in the "Great Weltkrieg". Bulgaria asked me for help, and I promised to guarantee their independence. The alliance probably didn't see me as a threat, since they went on with the war. Two front war wasn't really what Romanian and Serbian militaries could handle, basically I destroyed them both while Bulgarians were holding off the Greeks. Now, it's late 1941 and I control Croatia, Serbia and Romania as puppets. Kind of expecting to get attacked by Austria soon...