Though the Germans were initially behind the Poles and Soviets in their use of Armoured Trains, they soon recognised their usefulness for rear area security. The armoured trains came under the General of Panzer troops in 1941 and they remained mostly tied to security duties. However, by 1943 the armoured trains were increasingly engaged in frontline combat. This led to the development of the BP42 armoured train. By 1944 new specifications had been issued for German armoured trains. The BP44 was an up-armed version of the BP42. It replaced the older Polish guns with 10.5cm leFH18/40 howitzers and added further anti-tank weapons in the form of a Tank-hunter car at each end of the train. These were armoured flat cars mounting Panzer IV turrets. The Tankhunter cars were also added to the captured trains in German service. The Tank-hunter cars first began entering service in mid-1944.