During World War I (1914 to 1918), the Ceylon Defence Force was engaged in active service and the troops deployed in Galle and Matara too were mobilized.

The "B" Company in Galle and Matara was renamed the Ruhuna Volunteer Regiment in 1950 with Colonel C. A. Dharmapala, its first commanding officer.

Subsequently, the troops that were deployed in Galle formed the "C" Company of the 2nd [Vol] Battalion of the Sinha Regiment.

In the latter half of 1959, 110 soldiers deployed as "C" Company of the 2nd [Vol] Battalion, Sinha Regiment under the command of Capt.

Amarasuriya were brought together to form a new Volunteer Unit called the Gemunu Regiment, which was raised in Galle on 23 November 1959.

The nucleus of 1GW consisted of Officers and Other Rank Cadres drawn from the Regular Units already established.