Grant learned that Lee was sending part of his force to support Early in the Shenandoah Valley. He thought the Confederate trenches between Petersburg and Richmond were now more lightly defended. The information was wrong. But Grant saw an opportunity to break the siege of Petersburg by attacking the trenches around Deep Bottom. The week-long campaign failed to defeat the Confederate defenses because Grant had miscalculated the situation. He sent General Hancock with Union II Corps, X Corps, and General David McMurtrie Gregg’s cavalry division across the James at Deep Bottom during the night of August 13-14. At first, the Union attacks were successful. But soon Confederate reinforcements arrived and the Union advance stalled. On August 17 a truce was called so both sides could take care of their dead and wounded. Lee ordered a counterattack the next day. But it was poorly organized and did not accomplish much. Hancock, however, began a withdrawal of the Union troops north of James. By August 20 the withdrawal was completed. The Union forces maintained their bridgehead at Deep Bottom. Overall the battle and skirmishes cost the Union 3,000 casualties against a loss to the Confederacy of about 1,500. Lee's thinly defended line some long remained intact. But he could not afford to send any troops to Early in the Shenandoah Valley.