The Great War
Tannenberg
In a military convention with France, signed in 1913, the Russian Chief of the General Staff, General Jilinsky, pledged to put 800'000 men in the field by the 15th day of mobilisation. On the outbreak of war, two Russian armies advanced into East Prussia, a tongue of land projecting across the river Nieman to the heart of Russia, flanked on the north by the Baltic Sea and the south by Russian Poland. Jilinsky's plan was for First Army, commanded by General Pavel Rennenkampf, to advance against the eastern tip of East Prussia while his south, Second Army, led by General Alexander Samsonav, took the Germans at the rear, cutting off their line of retreat to the river Vistula.
The general commanding the German Eighth Army in East Prussia, Von Prittwitz, panicked. He was immediately replaced by General Enrich Von Ludendorff who, lacking the rank to hold supreme command, acted as Chief of Staff to a nominal superior, General Paul Von Hindenburg, who was brought out of retirement and made to squeeze into a uniform now too tight for him.
Even before Hindenburg and Ludendorff had arrived in East Prussia, the situation had been stabilised by one of Prittwitz's staff, Colonel Max Hoffman. He had exploited the gap between the two Russian armies, separated by the Masurian Lakes, to mount a delaying action in the north while concentrating in the south against Samsonov, whose sluggish advance was spread over a front of 60 miles. Ludendorff finished the job by enveloping Second Army and taking 125'000 prisoners. The unknown number of dead included Samsonov, who committed suicide on the 28th of august. The Germans then turned on First Army, which fell back in disorder after suffering a crushing defeat at the battle of the Masurian Lakes. German casualties in the two battles were fewer than 25'000 men!.