 Complete the following phrase:  At the outbreak of World War I Hoffmann became the first general staff officer of the German Eighth Army, responsible for defending their eastern border from a Russian attack. The bulk of the German Army, following the Schlieffen Plan, was attempting to gain decisive victory in the west by knocking France out of the war. Russian mobilization had begun secretly before the declaration of war, so earlier than anticipated the Russian First Army invaded East Prussia across its eastern frontier, the Eighth Army attacked them unsuccessfully at the 