Revolution Finds a Way

During the German invasion of Russia, a mysterious disease arose after a battle using a high amount of chemical weapons. All soldiers who contracted the disease dropped dead in an instant, and the disease was assumed extinct. But after a while the corpses of said soldiers rose back from the dead, and the true method of its spreading was discovered. Since then WWI has ended, once it did the Entante decided to check why Russia had surrendered so quickly, once they discovered the reason was a horde of zombies they immediately abandon Russia leaving the population to fend for themselves... and the revolutions began...