On August 17, 1914, the Russian First Army under General Paul von Rennenkampf and Second Army under General Alexander Samsonov invaded East Prussia and on the 20th defeated the Germans at Gumbinnen. However, the two generals strongly disliked each other and, knowing they would not come to each other's aid, German Colonel Max Hoffmann devised a plan of attack. The Russian First Army, which was moving very slowly to the north, would be ignored for the time being, and the German Eighth Army focused on the Russian Second Army. The East Prussian railway system would be used to rapidly transport troops, allowing the same German troops to be moved rapidly from one point to another. The Battle of Tannenberg began on August 26; by August 27 the Russians were falling back. By the 29th the Russians were encircled. By the conclusion of the battle on the 30th, the Russians had sustained 78,000 casualties, not including 92,000 who surrendered as prisoners of war. General Samsonov committed suicide. The Russian Second Army was destroyed as a fighting unit. Even though the battle was not particularly near Tannenberg (it was near Allenstein) it was given that name to counter a 1410 German defeat at Tannenberg. This was the first battle ever to see the use of airplanes for scouting purposes.