5 p.m., when he sent only two and a half brigades forward. Brig. Gen. Joseph B. Kershaw commanded the left flank, Brig. Gen. Paul J. Semmes the center, and Col. William Barksdale (Griffith's Brigade) the right. Franklin and Brig. Gen. John Sedgwick were on a reconnaissance to the west of Savage's Station when they saw Kershaw's brigade approaching. Their immediate assumption was that these were men from Heintzelman's corps, but they soon realized their mistake. This was the first indication of Heintzelman's unannounced departure and Sumner, for one, was particularly outraged, refusing to speak to Heintzelman the following day. Union artillery opened fire and pickets were sent forward to meet the assault. Magruder's attack was accompanied by the first armored railroad battery to be used in combat. Earlier in June, General Lee had hoped to counter the approach of McClellan's siege artillery by rail by using his own weapon: a 32-pounder Brooke naval rifle, shielded by a sloping casemate of railroad iron, nicknamed the "Land Merrimack." It was pushed by a locomotive at about the speed of the marching infantry. However, even with this impressive weapon, which outgunned anything the Federal artillerists possessed, the results of Magruder's decision to send only part of his smaller force against a much larger enemy were predictable. The first Union unit to engage was one of Sedgwick's brigades, Philadelphians led by Brig. Gen. William W. Burns, but his defensive line proved inadequate to cover the two brigade front of Kershaw and Semmes. Sumner managed this part of the battle erratically, selecting regiments for combat almost at random. He sent in two of Burns's regiments, and then the 1st Minnesota Infantry from another brigade in Sedgwick's division, and finally one regiment each from two different brigades in Brig. Gen. Israel B. Richardson's division. By the time all of these units reached the front, the two sides were at rough parity—two brigades each. Although Magruder had been conservative about his attack, Sumner was even more so. Of the 26 regiments he had in his corps, only 10 were engaged at Savage's Station. The fighting turned into a bloody stalemate as darkness fell and strong thunderstorms began to move in. The Land Merrimack bombarded the Union front, with some of its shells reaching as far to the rear as the field hospital. The final actions of the evening were by the Vermont Brigade, commanded by Colonel William