 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 