In August 1939, 49 RTR had still not received any tanks, so it mobilised as an infantry unit, and spent the Phoney War on guard duty in North East England.
At the end of May 1940, with the British Expeditionary Force being evacuated from Dunkirk and the imminent threat of German invasion of England, 25th Army Tank Brigade was redesignated 2nd Motor Machine Gun Brigade and its regiments reorganised accordingly.