Jack of Harts

When Germany finally accepted defeat and surrendered to the Allies, the German-Russian peace treaty was declared void.  Russia quickly moved to retake the lost regions, but the locals preferred independence and fought back.  Now known as the Russian Civil War, it waged for five years, killed millions of people, and destroyed their economy.  It birthed the Soviet Union, and while that nation would not survive the century, its legacy continues to this day.