The 1st New York Battery B went into action for the first time during the Siege of Yorktown. They eventually went on to fight in all of the battles of the Seven Days, seeing heavy action during II Corp's gallant defense at the Battle of Seven Pines. The regiment also saw fierce fighting during the massive artillery duel at the Battle of White Oak Swamp, and at the bloody repulse of the Confederates during the Battle of Malvern Hill. At the end of the Peninsula Campaign, Rufus D Pettit reported sick with "fatigue, exposure, and chronic diarrhea." These ailments had been bothering him most of his life, and would eventually force his discharge due to medical conditions.