Russian invasion of East Prussia (1914)
The Russian invasion of East Prussia occurred during World War I, lasting from August to September 1914. As well as being the natural course for the Russian Empire to take upon the declaration of war on the German Empire, it was also an attempt to focus the German Army on the Eastern Front, as opposed to the Western Front. Despite having an overwhelming superiority over the Germans in numbers, the invading Imperial Russian Army spread its forces thin and was defeated in the battles of Tannenberg and the Masurian Lakes, resulting in a complete strategic collapse of the Russian invasion.