The 11th Defense Battalion was commissioned on June 15, 1942 at Marine Corps Recruit Depot Parris Island, South Carolina.

[1] On August 26, 1942 the battalion was moved to Marine Corps Air Station New River, North Carolina.

After a month and a half in San Diego, California the battalion departed the United States on December 3, 1942.

[4] During July 1943, M3A1 Stuart Light Tanks of the 11th Defense Battalion were assigned to support the 43rd Infantry Division securing Munda Point on New Georgia.

[6] On July 13, 1943 another detachment was displaced when the 90 mm guns of Battery E were sent to support operations on New Georgia.

[8] On September 24, 1943 the battalion ceased operations at Purvis Bay and prepared for embarkation on naval shipping.

The entire battalion arrived on New Georgia on September 26 and immediately began emplacing near Ondonga Airfield.

During this time the battalion's Special Weapons Group was detached from the 40th Infantry Division on Guadalcanal.