The Cossacks are Coming! is an operational simulation of the World War I Tannenberg campaign in which Russian and German armies battled during August and September of 1914. The game uses weekly turns (each composed of a variable number of impulses), a map scale of five miles per hex, and battalion to brigade level units to portray the conflict. Aspects of the campaign covered by the rules include artillery, limited intelligence, reconnaissance, command control, supply, morale, and prisoners of war.