Buckinghamshire Light Infantry, a Regular Army unit, and transferred to the 11th Infantry Brigade, of the 4th Infantry Division. This was official policy within the BEF and was, in theory, intended to strengthen the inexperienced Territorial divisions with experienced Regulars. France and Dunkirk When the Germans invaded France and the Low Countries on 10 May 1940, the BEF moved forward to occupy pre-planned positions in Belgium, but the rapid German breakthrough into France caused it to retreat towards Dunkirk. On 23 May, 48th Division was pulled out to form a new defence line along the canal between Saint-Omer and the coast. The divisional Commander, Royal Artillery, Brigadier Edward Lawson, was sent with 'X Force' of artillery, machine guns and infantry ahead of the division to occupy the chosen positions. However, the unexpected surrender of Belgian forces on 27 May 1940 led to a gap appearing between 48th Division in action around Saint-Omer and the coast at Nieuwpoort. Until II Corps could arrive to plug this gap, Lawson was responsible for what the Official History calls 'the most dangerously exposed part of the bridgehead'. He was ordered by the commander of the Dunkirk perimeter, the III Corps commander Lieutenant-General Ronald Adam, to improvise a defence line along the canal and prevent the Germans breaking through to the vital beaches east of Dunkirk where much of the BEF was waiting to be evacuated. At 11.00 on 28 May, advanced German troops reached the canal line, but Lawson seized on the Territorial gunners of the 53rd (London) Medium Regiment, RA who were marching towards Dunkirk having fired off all their ammunition and destroyed their guns. Together with detachments of Regular gunners from both the 2nd Medium and 1st Heavy Anti-Aircraft Regiments, and sappers from 7th Field Company, Royal Engineers, they fought as infantry to hold the line. They came under heavy mortar and machine gun fire, and the Germans seized a bridgehead at Nieuwpoort, but all subsequent attacks that day were repulsed. Brigadier Lawson's scratch force was relieved next day and then evacuated to Britain. Home defence and training The 48th Division, much depleted in numbers, completed its return to the United Kingdom on 1 June. The division, commanded from 18 June by Major General Roderic Petre, was subsequently posted to Western Command, Southern Command, and VIII Corps under Lieutenant General Harold Franklyn and began training in preparation to repel Operation Sea Lion,