What was the outcome of the Battle of Tannenberg?
The battle of Tannenberg (August 1914) was fought, during WWI, between Germans and Russians resulting in the victory of the German Army.
The battle of Tannenberg was fought basically between the German 8th army and the advancing Russian 2nd Army. The outcome was the almost complete destruction of the 2nd army (its commander Gen. Samsonov even committed suicide).
The battle was orchestrated by the two masterminds of German Strategy/Tactics in WWI, Gen. Hindenburg and Gen. Ludendorff (that they will become, after the exit of Russia from the war, commanders in the west).
In total, over 50,000 Russian soldiers were killed and some 92,000 taken as prisoners in the Battle of Tannenberg.
[Russian Prisoners taken at Tannenberg]
One of the reasons for the defeat (and slaughter) of the Russian 2nd Army was the incredible blunder of the Russian commanders sending each other un-coded messages explaining their tactics and intentions (Samsonov was informing his colleague of the 1st Army, in the north, of his intentions and plans)! Needless to say that the Germans intercepted the messages, read them and had a perfect view of the situation enabling them to maneuver and trap the Russians.
An anecdote (so take it as absolutely NOT confirmed) says that General Ludendorff had a nerve collapse induced by the doubt that the messages, not coded and so perfectly readable, could be a trap of the Russians!