They were rejected by the U.S. Marine Corps in 1939, but after the attack on Pearl Harbor they were exported and used as an emergency light tank.

It primarily served in Alaska and the Dutch East Indies, while small numbers were used in the U.S. as guard tanks stationed along the U.S. coast.

[1] With a crew of two, consisting of the driver and gunner,[2] and protected by up to 0.5 in (12.7 mm) of armor, it was named the Combat Tank Light 3 (CTL-3).

Tests continued until 1940,[3] after which the Marine Corps deemed it obsolete because of the goals to make it amphibious which left it with fragile tracks and weak armor.

[3] A small number were used by the US Marine Corps' 1st Tank and 1st Scout Companies prior to the war.

After the attack on Pearl Harbor, the Ordnance Committee determined that a few CTLS-4TAC and 4TAYs would be dispersed to the U.S. Army and employed in the Aleutian Islands campaign.

[3] Several hundred CTMS tanks were ordered by the Royal Netherlands East Indies Army.

As more robust light tanks were already being produced in sufficient numbers, the US Army officially declined the CTMS-1TB1, in May 1943.

[11] The US government also leased a few dozen examples of the CTMS-1TB1 to Latin American countries, including Mexico, Guatemala, Ecuador and Cuba.

[11] The MTLS-1G14 project was started at the same time as the CTMS-1TB1 to produce a four-man medium tank for the Dutch Army.