Lee finally gave in to the pressure and abandoned both cities on April 3, 1865. This led to Lee's final surrender at Appomattox Court House on April 9, 1865. The trench warfare of Petersburg became common in World War I, earning it a prominent position in military history. Of the 4,000 African American troops of the 4th Division, IX Corps, who fought at the Battle of the Crater on July 30, 1864, over half were killed, wounded or captured.