Grand Duke Nicholas's primary objective was saving Second Army and avoiding a repeat of the disaster at Tannenberg. On 16 November he ordered Wenzel von Plehve's Russian Fifth Army to abandon the proposed offensive into Silesia and to move northward towards Łódź; they marched in only two days. As soon as Hindenburg saw the transcript of this order, he knew that his maneuver had succeeded. Now seven Russian corps were defending the city. Plehve smashed into Mackensen's right flank on 18 November in bitter winter conditions (at times the temperature dropped as low as .