During the evening of 7 August 1944, the attacking forces formed up in six columns, four vehicles wide, comprising tanks, Kangaroo APCs, half tracks, self-propelled anti-tank guns and Mine flail tanks. At 23:00, Bomber Command commenced the bombardment of German positions along the Caen front. At 23:30, the armoured columns began their advance behind a rolling barrage. Movement was slow at first, many APC drivers became disoriented by the dust caused by the vehicles. Several vehicles became stuck in bomb craters. Simonds had arranged several methods for the columns to maintain direction; some vehicles were fitted with radio direction finders, the artillery fired target-marking shells, Bofors 40 mm guns fired bursts of tracer in the direction of the advance. In spite of all these measures, there was still confusion. Several vehicles collided or were knocked out.