Pictures are of the "Krummlauf'" attachment to the MP 44, designed not merely to fire round corners (a requirement arising from street fighting in Italy), but also for use in tanks. Russian infantry swarming over "closed-down" German tanks in battle were often found to be inaccessible targets to weapons fired through the pistol ports on the tanks. To dislodge them some sort of hose-pipe weapon was needed. (Similar circumstances reported by U.N. troops in Korea a decade later led to the experimental resurrection of this German innovation.) It is clear that if the weapons were provided with a periscopic sight as shown the infantry could remain fully concealed whilst shooting from trenches and foxholes. The attachment was the fruit of experiments, carried out in Germany during the early 1940s, with the object of providing a device which would enable troops to shoot from behind cover, without exposing themselves to enemy fire. Various deflecting troughs and curved barrels were tried with a number of infantry weapons, before this combination was arrived at. The relatively short bullet fired by the MP44 made it particularly suitable for this role. The attachment deflects the flight of the bullet through 30 degrees and, with the aid of the prismatic sight which is fitted, a reasonable degree of accuracy can be attained. A further version of the device was developed which deflected the bullet through 90 degrees. This was intended for use as a close-defence weapon by armoured vehicle crews; however it was found that bullets fired through it generally fragmented due to the stresses involved. The curved barrel device has proved something of a technological dead-end. By contrast, the rifle itself was of fundamental importance in the development of modern military firearms, being the first "assault rifle" to see widespread use. The assault rifle concept grew from a realization that the ammunition fired by conventional rifles was too powerful for normal combat use. It could kill at over 2000 metres, but First World War experience showed that infantry firefights seldom occurred at ranges in excess of 400 metres. Consequently it was perceived that smaller and less powerful cartridges could be used. Although such thinking was current in several countries, Germany was the first to put it into practical effect. Using a shortened version of the standard rifle cartridge, the German assault rifle was able to deliver controllable fully-automatic fire against close-range targets, while still offering the possibility of accurate aimed fire out to all normal combat ranges. This development revolutionized the infantryman's armament, rendering conventional rifles and submachine-guns obsolescent. The concept was soon taken up by other nations, most notably by the Soviet Union with the famous Kalashnikov Avtomat (AK47). Assault rifles are now standard equipment in armies throughout the world.