 The regiment participated in McClellan's Peninsular campaign of 1862 and suffered its worst casualties to date at the Battle of Seven Pines, Virginia, on May 31, 1862, and at Groveton (or Second Bull Run) on August 29, 1862.The Third Michigan infantry played a peripheral part in the battle of Fredericksburg on December 13, 1862.The next major action for the regiment was at Chancellorsville, Virginia, on May 3, 1863, followed by Gettysburg where the Third found itself exposed in the Peach Orchard on July 2, 1863.