During the night of July 4-5th, General Robert E. Lee's battered army began its retreat from Gettysburg, moving southwest toward Hagerstown and the Potomac River crossing at Williamsport, screened by Maj. Gen. J. E. B. Stuart’s cavalry. Lee’s infantry reached the rain-swollen Potomac but could not cross, the pontoon bridge having been destroyed by a cavalry raid. On July 11th, Lee entrenched a line protecting the river crossings at Williamsport and waited for Maj. Gen. George G. Meade’s army to advance. On July 12th, Meade reached the vicinity and probed the Confederate line. The next day skirmishing was heavy along the lines as Meade positioned his forces for an attack. In the meantime, the river fell enough to allow the construction of a new bridge, and Lee’s army began crossing the river after dark on the 13th. On the morning of the 14th, two Union cavalry divisions attacked the rearguard division of Brig. Gen. Henry Heth still on the north bank, taking more than 500 prisoners. Confederate Brig. Gen. James Pettigrew was mortally wounded in the fight. Lee's army was safely back in Virginia. Meade had let his best chance to destroy the Army of Northern Virginia slip away from him. In Washington, a frustrated Abraham Lincoln reportedly said, "We had them within our grasp." The war in Virginia would go on nearly two more years.