Tremlett's next action was the Peninsula Campaign. From April through July, 1862, he was part of an enormous force of approximately 121,000 troops that General George McClellan landed at Fort Monroe on the Virginia peninsula. McClellan's plan was to seize Richmond and thereby end the war, but instead he was turned back by General Robert E. Lee and eventually McClellan's entire army was driven from the peninsula. Tremlett's regiment fought at Eltham's Landing, Seven Pines, Oak Grove, Mechanicsville, Gaines' Mill, Savage's Station, Glendale, and Malvern Hill.