"he will be called up for military service"

The 8th Royal Scots
Public DomainThe 8th Royal Scots
With the enactment of the National Service (Armed Forces) Act of 1939, British men between 18 and 40 could be called up at any time for military service. The age limit was raised to 51 in 1941, and single women between 20 and 30 were added to the list of those required to perfom some sort of war service.