The Battle of Stallupönen, fought between Russian and German armies on August 17, 1914, was the opening battle of World War I on the Eastern Front. The Germans under the command of Hermann von François conducted a successful counterattack against four Russian infantry divisions from different infantry corps, which heavily outnumbered them but were separated from each other, creating a gap between the 27th Infantry Division and the 40th Infantry Division, and had little coordination with each other. The Germans retreated to Gumbinnen thereafter.