The Russian propensity for using unencrypted communications helped the implementation of General Hindenburg’s masterplan for the Battle of Tannenberg. It was established that the Russian General Rennenkampf’s 1st Army was moving on Konigsberg away from Samsonov’s 2nd Army. Hindenburg was then able to plan with some exactitude his attack on the 2nd Army by learning the precise route Samsonov intended to take, in what he believed to be the pursuit of a demoralized and retreating German Army. Able to leave a token force of cavalry and Landwehr to stall any attempt at rescue from Rennenkampf, Hindenburg’s 8th Army completed the encirclement of the 2nd Army on 26–30 August. What followed was a rout of Samsonov’s army of 150,000 men. Only about 10,000 men escaped and 60 trains were required to transport all the captured weaponry back to Germany. Samsonov committed suicide after the catastrophic defeat.
— OR —