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 brigade's previous commander, Kenneth Anderson, had been promoted to General Officer Commanding (GOC) 3rd Division during the evacuation, when Lieutenant-General Alan Brooke, commander of II Corps, was recalled to the United Kingdom and Montgomery took over the corps. On Horrocks' return to Britain, he was given command of 9th Brigade and assigned to defend against a possible German invasion. A short stint as Brigadier General Staff of Western Command followed, before promotion to acting major-general and command of the 44th (Home Counties) Infantry Division on 25 June 1941. He was promoted to substantive colonel on 28 May 1941 (with seniority backdated to 1 July 1940). The 44th Division, composed of the 131st (Surrey), 132nd (Kent) and the 133rd (Sussex) Infantry Brigades together with supporting units, was stationed in Kent preparing to repel the expected German invasion of the United Kingdom. The division was responsible for the southern Kent coast east of Folkestone and was serving under the command of XII Corps, commanded by Montgomery, who secured for Horrocks his new command. In March 1942, Horrocks was given command of the newly formed 9th Armoured Division and gained the temporary rank of major-general on 27 June. Horrocks, an infantry soldier with no experience in dealing with cavalry, was an unusual choice for commander of an armoured division. He trained the division hard, organising exercises to improve the effectiveness of his troops, and to familiarise himself with armoured warfare. Despite never having commanded a division in battle, he was further promoted to acting lieutenant-general and sent to Egypt to command the Eighth Army's XIII Corps, under Montgomery. General Sir Harold Alexander and Lieutenant-General Montgomery had decided to make a "clean sweep" when replacing the dismissed Claude Auchinleck as Commander-in-Chief (C-in-C) Middle East and Eighth Army commander respectively. Officers perceived to have failed under the old regime were removed, and Montgomery's favoured commanders were brought in. Among these