In July, the Second Maryland was dispatched along with the rest of Burnside's command to aid in Maj. Gen. George McClellan's foundering Peninsula Campaign outside of Richmond, arriving shortly after the Battle of Cedar Mountain.

The information confirmed that Confederate General Robert E. Lee had turned his attention to the Union Army of Virginia—headed by Maj. Gen. John Pope—and allowed Pope to shift his forces to meet the new threat.

On the afternoon of the 29th, the Second Maryland, as part of James Nagle's brigade in Burnside's IX Corps, assaulted troops under the command of Confederate General T. J.

Union commander George B. McClellan had tasked Burnside with opening up a southern front to the battle to divert Confederate forces from a simultaneous attack taking place on the north end of the field.

After traveling for several hundred yards down a road running parallel to the creek, and open to flanking fire the entire way, Nagle's brigade, with the 2nd Maryland and 6th New Hampshire in the vanguard, broke before reaching the bridge.

[citation needed] The Second saw limited action at Fredericksburg, where they were held in reserve for most of the day before making a late assault on a stonewall at the base of Marye's Heights manned by Confederate forces.