fall of 1861, Dimon assisted in the recruitment of a new regiment which would become the 30th Massachusetts Infantry. The regiment was one of several being raised by Maj. Gen. Benjamin Butler for his planned expedition to take New Orleans, Louisiana, the largest city in the Confederacy. The regiment left Massachusetts on January 2, 1862, arrived off the Louisiana coast in mid February, and played a minor role in the Siege of New Orleans in April and May 1862. Early in his service with the 30th Massachusetts, Dimon caught the attention of Maj. Gen. Butler who was impressed with the young man's energy and enthusiasm. Through Butler's influence, Dimon was commissioned 1st lieutenant on February 20, 1862, and given the position of regimental adjutant—an administrative role assisting Colonel Nathan Dudley, the commanding officer of the regiment. Serving with the 30th Massachusetts, Dimon played a role in the regiment's efforts, in July 1862, to dig a canal opposite Vicksburg, Mississippi (the major Confederate stronghold on the Mississippi River). The aim was to redirect the river and circumvent Vicksburg, thus opening the Mississippi to the Union. The effort was unsuccessful, however, and the 30th's brigade marched to Baton Rouge, Louisiana, at the end of July. On August 5, 1862, Dimon and the 30th Massachusetts saw their first heavy combat during the Battle of Baton Rouge as the Confederates unsuccessfully attempted to recapture the state capital. 2nd Louisiana In September 1862, the 2nd Louisiana Infantry, a unit of Louisiana unionists and former Confederate prisoners-of-war was formed. Again, through Butler's sponsorship, Dimon was promoted to major and assigned to the 2nd Louisiana as third-in-command, serving under Col. Charles Jackson Paine. The 2nd Louisiana saw action during the Battle of Plains Store, and the Siege of Port Hudson in the spring and summer of 1863. After the second assault on Port Hudson in June 1863, Maj. Dimon fell ill and was discharged due to disability on June 22, 1863. 1st United States Volunteers After his recovery, in early 1864, Dimon sought a position on the staff of Maj. Gen. Butler, who was then in command of the Department of Virginia and North Carolina with headquarters at Fortress Monroe. Instead of placing Dimon on his staff, Butler appointed him as major of a new regiment, the 1st United States Volunteer Infantry, then being formed under Butler's supervision. The regiment, organized at the prisoner-of-war camp at Point