 Complete the following phrase:  Upon arriving at Marienberg on 23 August, Hindenburg and Ludendorff were met by members of the 8th Armys staff led by Lieutet Colonel Max Hoffmann, an expert on the Russian army. Hoffman informed them of his plans to shift part of the 8th Army south to attack the exposed left flank of the advancing Russian Second Army. Agreeing with Hoffmans strategy, Hindenburg authorized Ludendorff to transfer most of the 8th Army south while leaving only two cavalry brigades to face the Russian First Army in the north. In Hindenburgs words the line of soldiers defending Germanys border against was thin, but not weak, because the men were defending their homes. If pushed too hard by the Second Army, he believed they would cede ground only gradually as German reinforcements continued to mass on the invading Russians flanks before ultimately encircling and annihilating them. On the eve of the ensuing battle, Hindenburg reportedly strolled close to the decaying walls of the fortress of the Knights of Prussia, recalling how the Knights of Prussia were defeated by the Slavs in 1410 at nearby 