The genesis of APDS was development by engineers working for the French Edgar Brandt company of saboted ammunition, in which a sub-calibre core was surrounded by a lightweight 'sabot' (from the French term 'shoe') that was retained by the round for the duration of its time in flight until impact, and was fielded in two calibers (75 mm/57 mm for the Mle1897/33 75 mm anti-tank cannon, 37 mm/25 mm for several 37 mm gun types) just before the French-German armistice of 1940. The Edgar Brandt engineers, having been evacuated to the United Kingdom, joined ongoing anti-tank ammunition development efforts there, culminating in significant improvements to the concept and its realisation. Whilst the adoption of the sabot improved the performance of the ammunition, the retention of the sabot until impact contributed additional drag that caused the performance of the shot to fall off dramatically with increasing range. What was needed was a sabot that could be discarded after leaving the barrel so that the smaller, heavier, sub-projectile could carry on at the much higher velocity imparted to the whole round while suffering less drag due to the smaller diameter and hence lower frontal area. The resulting APDS - the 'D' standing for 'discarding', projectile type was developed in the United Kingdom between 1941–1944 by Permutter and Coppock, two designers with the Armaments Research Department (ARD). In mid-1944 the APDS projectile was introduced into service for the UK's QF 6 pounder anti-tank gun and later in September 1944 for the QF 17 pounder anti-tank gun.