Where was the Eastern Front located?

In World War I, the Eastern Front essentially consisted of the borders between Austria-Hungary, Germany and Bulgaria on the west, and Russia and Romania on the east. In World War II, the Eastern Front extended from Germany's border with Poland in the north to Ukraine's border on the Black Sea.

During World War I, fighting on the Eastern Front ended in 1917, when the Communist Revolution ended Russia's involvement in the war. In World War II, fighting along the front was much more protracted, and it involved a massive push deep into Russian territory that proved disastrous for an overextended German army.