In January 1938, Hibbert was commissioned into the Royal Artillery. On 9 September 1939, less than ten days after the German invasion of Poland, he arrived in Cherbourg, France, with the British Expeditionary Force. In the Battle of Dunkirk, he commanded a half-battery that defended the Allies' northern perimeter for four days. On 1 June 1940, his ammunition supply depleted, he was forced to destroy his guns. Evacuated from Dunkirk on the tugboat "Sun X", Hibbert was mentioned in dispatches that described his meritorious actions in the face of the enemy and were sent to the high command.