Following the outbreak of the Second World War in September 1939, Watkins joined the British Army as a private in the Duke of Cornwall's Light Infantry in October 1939. After serving for over a year as a private he was sent for officer training and was commissioned, with the rank of second lieutenant, into the Welch Regiment on 17 May 1941. He was given the service number 187088. He was posted to the regiment's 1st/5th Battalion, a Territorial Army (TA) unit. The battalion was one of three (the others being the 4th Welch Regiment and the 2nd Monmouthshire Regiment) which formed part of the 160th Infantry Brigade, itself being one of three brigades (the others being the 158th and 159th) forming the 53rd (Welsh) Infantry Division. The division, then commanded by Major General Gerard Bucknall, was serving in Northern Ireland until moving to Wales late in 1941, and then to Kent in April 1942, where it remained for over two years before it was to see any action, until then being engaged in numerous military exercises and training and learning the art of war.