On June 25, 1862, McClellan ordered an ineffective offensive triggering the Seven Days Battles. On June 26, General Robert E. Lee, who had recently taken command of the Army of Northern Virginia, launched a daring counter-offensive intended to drive McClellan's army away from Richmond. For the 22nd, the third day of the Seven Days Battles, the Battle of Gaines' Mill, proved to be devastating as they suffered their worst casualties of the war.