 Complete the following phrase:  At the outbreak of the Second World War, Horrocks was working as an instructor at the Staff College, Camberley, where he had taught since 1938. After helping organise a new, shorter, officer-training course, in December 1939 he was promoted to substantive lieutet colonel. The following May, he was despatched to France to command the 2nd Battalion, Middlesex Regiment, a machine-gun battalion directly subordinate to the 3rd Division headquarters of Major-General Bernard Montgomery. British doctrine at the time retained heavy machine guns under the direct command of a corps or division, rather than as an organic part of subordinate formations. He joined the battalion during its retreat to Dunkirk, and after only 17 days had impressed his superiors sufficiently to be given the temporary rank of brigadier, and the command of 11th Brigade. The brigades previous commander, Kenneth Anderson, had been promoted to General Officer Commanding GOC 3rd Division during the 