The regiment was attached to 1st Brigade, Department of the Gulf, to October 1862.
2nd Brigade, 1st Division, XIX Corps, Department of the Gulf, to August 1863.
The regiment left Connecticut for Ship Island, Mississippi on February 24, 1862.
They filled duty assignments at Ship Island, Mississippi, until April 15, 1862.
Operations against Fort St. Phillip and Jackson, Mississippi River, April 15–28.
Expedition to Lake Pontchartrain, Pass Manchac, and up Tchefuncta and Pearl rivers July 25-August 2.
Moved to Brashear City, Louisiana February and duty there until March.
Philip Sheridan's Shenandoah Valley Campaign, August to December.
In late-September 1862 while stationed at Camp Parapet, a lieutenant in the 12th Connecticut, George H. Hanks, was detailed as aide-de-camp for Brigadier General Thomas W. Sherman for the superintendence of the many contraband arriving at the camp.
He organized six colonies of freedmen at Camp Parapet each led by a non-commissioned officer and directed black labor in the repair and fortification of the camp and surroundings.
[1] Hanks was transferred out of the regiment January 1, 1863 and made a member of the Army officer corps.
[2] Hanks's assistant superintendent was another member of the regiment, Philip Bacon.