pushed the Confederates back to their original lines, secured advanced positions and cut the Confederates access to direct communication with Pickett over White Oak Road and the Boydton Plank Road. After securing his position, Warren also was able to send units to outflank and drive off Pickett's forces which were in a position to inflict a serious defeat on Sheridan's troopers whom Pickett's force had pushed back that day at Dinwiddie Court House. The battles at White Oak Road and Dinwiddie Court House, while initially successful for the Confederates, even a tactical victory at Dinwiddie, ultimately did not advance their lines or achieve their strategic objective of weakening and driving back the Union forces or separating Sheridan's force from support. The battles and their aftermath set the stage for the Confederate defeats and the collapse of Confederate lines at the Battle of Five Forks on the following day, April 1, 1865, and the Third Battle of Petersburg (also known as the Breakthrough at Petersburg) on April 2, 1865 and ultimately led to the surrender of Lee's Army of Northern Virginia after the Battle of Appomattox Court House, Virginia on April 9, 1865. Background Military situation Siege of Petersburg When two unobserved corps of the Union Army of the Potomac, which combined with the Union Army of the James outside Petersburg, failed to seize the city from a small force of Confederate defenders at the Second Battle of Petersburg, the 292-day Richmond–Petersburg Campaign (Siege of Petersburg) began. Union General-in-Chief Ulysses S. Grant had to conduct a campaign of trench warfare and attrition in which the Union forces tried to wear down the less numerous Confederate Army, destroy or cut off sources of supply and supply lines to Petersburg and Richmond and extend the defensive lines which the outnumbered and declining Confederate force had to defend to the breaking point. After the Battle of Hatcher's Run on February 5–7, 1865 extended the lines another , Lee had few reserves after manning the lengthened defenses. Lee then knew that part or all of his army must leave the Richmond and Petersburg lines, obtain food and supplies at Danville, Virginia or possibly Lynchburg, Virginia and join General Joseph E. Johnston's force opposing Major General William T. Sherman's army in North Carolina. If the Confederates could quickly defeat Sherman, they might turn back to oppose Grant before he could combine his forces with Sherman's. Lee