At the outbreak of the Second World War in September 1939 Templer was an acting lieutenant-colonel, and, on 4 September, the day after war was declared, he was chosen to be one of two GSO1s to the DMI of the British Expeditionary Force (BEF), Major-General Noel Mason-MacFarlane, replacing the original choice, Kenneth Strong. He soon found himself in France. Templer's duties were mainly concerned with counter-intelligence and security. The German Army attacked in the West on 10 May 1940, although Templer himself was then on leave but was back in France and discovered Mason-MacFarlane was in Brussels, with the intelligence staff moving behind him but was a long distance from GHQ BEF, resulting in poor communications. On 17 May General Lord Gort, the BEF's Commander-in-Chief (C-in-C), feared for the BEF's right flank along the River Scarpe and, due to a shortage of troops, ordered Mason-MacFarlane to form "Macforce" to hold the river with whatever troops could be found. Templer subsequently became GSO1 of "Macforce". The only unit of any size then available was Brigadier John Smyth's 127th Brigade, detached from its parent 42nd Division, which was soon strengthened by armoured cars of Lieutenant-Colonel George Hopkinson's "Hopkinson Mission", and some scattered artillery and engineer units. The 127th Brigade was soon replaced by the 139th Brigade (also detached its parent 46th Division) and "Macforce" continued taking on scattered units and, after a few small skirmishes but no major engagements, was eventually disbanded. With the BEF retreating to Dunkirk, both Mason-MacFarlane and Templer were evacuated to England, arriving there on 27 May.