Lee's intricate plan went awry immediately. Jackson's men, fatigued from their recent campaign and lengthy march, ran at least four hours behind schedule. By 3 p.m., A.P. Hill grew impatient and began his attack without orders. Hill's division, minus Brig. Gen Lawrence O'Brian Branch's brigade, which was placed off to the north to link up with Jackson, entered Mechanicsville and skirmished with George McCall's Union division, deployed around the town. McCall fell back to an easily defensible spot on the opposite side of Beaver Dam Creek. There, the brigades of Brig. Gen John F. Reynolds and Brig. Gen Truman Seymour dug in, with Brig. Gen George G. Meade's brigade placed behind them in reserve, Reynolds' brigade to the north and Seymour's to the south. On Reynolds' right, the divisions of Brig. Gen George Morell and Brig. Gen George Sykes formed a semicircle. Supporting the roughly 26,000 Union infantrymen were 32 artillery pieces. There, 14,000 well entrenched infantry, supported by 32 guns in six batteries, repulsed repeated Confederate attacks with substantial casualties.