Grant and Meade's Army of the Potomac crossed the Rappahannock River and entered the area known as the Wilderness. On May 5, 1864, Grant was met by an undersize Confederate force of 60,000 soldiers led by Lee. At the bloody but tactically inconclusive Battle of the Wilderness (May 5–7) and Battle of Spotsylvania Court House (May 8–21), Grant failed to destroy Lee's army. But, unlike his predecessors, Grant did not retreat after the battles. He repeatedly moved his army leftward to the southeast in a campaign that kept Lee on the defensive and moved ever closer to Richmond. Grant spent the remainder of May maneuvering and fighting minor battles with the Confederate army as he attempted to turn Lee's flank and lure him into the open. Grant knew that his larger army and base of manpower in the North could sustain a war of attrition better than the Confederacy could. This theory was tested at the Battle of Cold Harbor (May 31 – June 12) when Grant's army once again came into contact with Lee's near Mechanicsville. He chose to engage Lee's army directly, by ordering a frontal assault on the Confederate fortified positions on June 3. This attack was repulsed with heavy losses. Cold Harbor was a battle that Grant regretted more than any other and Northern newspapers thereafter frequently referred to him as a "butcher". Although Grant suffered about 45% casualties. Lee lost about 50% his forces. These were losses that Lee could not replace.