 Complete the following phrase:  The invading forces made a determined and speedy attack on East Prussia. However, the First and Second Armies were stopped by the German Eighth Army, led by Field Marshal Paul von Hindenburg and his chief of staff, General Erich Ludendorff. The German and Russian armies met at Tannenberg, where the Second Army was encircled and suffered complete destruction. Both the First and Second Armies suffered terrible casualties in one of the most comprehensive German victories of World War I. The First Army also suffered defeat at the 