After failed opening assaults to capture Petersburg during June 15-18, 1864, Lieutenant General Ulysses Grant sought another attempt against the city and its supply lines while he still held the initiative. General George Meade ordered the Army of the Potomac's II Corps, under temporary command of General David Birney, and General Horatio Wright's VI Corps to leave their trenches east of Petersburg and maneuver west of the Jerusalem Plank Road in a northwesterly direction to capture the Weldon and Southside Railroads, with the hope of breaking those supply lines and reaching the Appomattox River west of Petersburg. On June 21, 1864, Meade instructed Birney to move on the left of the Fifth Corps, extend as far left as practicable, keep close to the enemy's line, and try to seize the Weldon Railroad, while the Sixth Corps was to take position on Birney's left and help stretch the line toward the Appomattox. After probing operations on June 21st, the main Union movement began on the morning of June 22nd, with the II Corps on the right pivoting from the Union works along the Jerusalem Plank Road toward the northwest. The VI Corps on the left failed to maintain contact with Birney's corps as it moved through swampy thickets and wooded terrain, and Meade ordered Birney to continue because the VI Corps was lagging, saying that each corps must look out for itself. The resulting large gap between the two forces gave the Confederates an opportunity to exploit it.