After the victories of Fredericksburg and Chancellorsville, Lee decided to cross the Potomac again and invade the north once more. When Lee found out that a large Union force under the command of General George G. Meade, who had replaced General Joseph Hooker, was at Frederick, Maryland, Lee decided to center his forces at Gettysburg, Pennsylvania. On July 1, 1863, the Confederate forces attacked Meade's forces and made temporary gains. Two days later, three Confederate brigades commanded by General George E. Pickett advanced to the Federal cannon center, now called Cemetery Ridge, where mass slaughter of the Confederates took place. On July 4, the remaining Confederates returned sadly across the Potomac River into Virginia. Approximately two weeks after the Gettysburg defeat, a surprise attack on Wytheville, Virginia, was thwarted by the courageous efforts of Molly Tyres who rode rapidly over forty miles of mountain road between Tazewell and Wytheville to warn the inhabitants of the coming attack. Thus, did Virginians--military and civilian--strive to help the Confederate cause in which they so strongly believed. On May 5 and 6, 1864 the so-called Battle of the Wilderness was fought in the heavily forested terrain of Spotsylvania County. As General R. S. Ewell was returning his forces from Fredericksburg to Orange, he encountered General Ulysses S. Grant who had become commander of the Union army. At the same time forces under General Ambrose P. Hill encountered the left wing force under Grant which resulted in terrific fighting within the dense woods of the wilderness. As the left wing force under Grant was breaking through the forces under Hill, General James Longstreet approached and forced the Union troops back to Spotsylvania Courthouse, southwest of Fredericksburg. Grant retreated in this direction in an attempt to keep Lee away from Richmond. However, Lee was ahead of Grant. Although Grant tried repeatedly from May 8 to May 18 to break through the Confederate lines at Spotsylvania with exceptionally heavy musketry fire causing thousands of casualties, he was unable to penetrate Lee's lines. Therefore, he moved southward to the North Anna River. In the meantime, on May 10, when General Philip Sheridan tried to make an unexpected rush on Richmond, "J.E.B." Stuart, with only part of his cavalry, blocked Sheridan's way at Yellow Tavern and saved the Confederate capital. Stuart was mortally wounded by a close pistol shot in this fighting and he died on May 11, 1864 in Richmond. He is considered by many military strategists as the greatest cavalryman in United States history.