During the Civil War, Ulysses S. Grant's Army of the Potomac and Robert E. Lee's Army of Northern Virginia collide for the last time as the first wave of Union troops attacks Petersburg, a vital Southern rail center 23 miles south of the Confederate capital of Richmond, Virginia. The two massive armies would not become disentangled until April 9, 1865, when Lee surrendered and his men went home.
In June 1864, in a brilliant tactical maneuver, Grant marched his army around the Army of Northern Virginia, crossed the James River unopposed, and advanced his forces to Petersburg. Knowing that the fall of Petersburg would mean the fall of Richmond, Lee raced to reinforce the city's defenses. The mass of Grant's army arrived first. On June 15, the first day of the Battle of Petersburg, some 10,000 Union troops under General William F. Smith moved against the Confederate defenders of Petersburg, made up of only a few thousand armed old men and boys commanded by General P.G.T. Beauregard. However, the Confederates had the advantage of formidable physical defenses, and they held off the overly cautious Union assault. The next day, more Federal troops arrived, but Beauregard was reinforced by Lee, and the Confederate line remained unbroken during several Union attacks occurring over the next two days.
By June 18, Grant had nearly 100,000 at his disposal at Petersburg, but the 20,000 Confederate defenders held on as Lee hurried the rest of his Army of Northern Virginia into the entrenchments. Knowing that further attacks would be futile, but satisfied to have bottled up the Army of Northern Virginia, Grant's army dug trenches and began a prolonged siege of Petersburg.
Finally, on April 2, 1865, with his defense line overextended and his troops starving, Lee's right flank suffered a major defeat against Union cavalry under General Phillip Sheridan, and Grant ordered a general attack on all fronts. The Army of Northern Virginia retreated under heavy fire; the Confederate government fled Richmond on Lee's recommendation; and Petersburg, and then Richmond, fell to the Union. Less than a week later, Grant's massive army headed off the remnants of the Army of Northern Virginia at Appomattox Station, and Lee was forced to surrender, effectively ending the Civil War.