The V-2 (German: Vergeltungswaffe 2, "Retaliation Weapon 2"), with the technical name Aggregat 4 (A4), was the world's first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was developed during the Second World War in Germany as a "vengeance weapon" and assigned to attack Allied cities as retaliation for the Allied bombings against German cities. The V-2 rocket also became the first artificial object to travel into space by crossing the Kármán line with the vertical launch of MW 18014 on 20 June 1944.Research into military use of long-range rockets began when the graduate studies of Wernher von Braun attracted the attention of the German Army. A series of prototypes culminated in the A-4, which went to war as the V-2. Beginning in September 1944, over 3,000 V-2s were launched by the German Wehrmacht against Allied targets, first London and later Antwerp and Liège. According to a 2011 BBC documentary, the attacks from V-2s resulted in the deaths of an estimated 9,000 civilians and military personnel, and a further 12,000 forced laborers and concentration camp prisoners died as a result of their forced participation in the production of the weapons.The rockets travelled at supersonic speed, impacted without audible warning, and proved unstoppable, as no effective defense existed. Teams from the Allied forces—the United States, the United Kingdom, and the Soviet Union—raced to seize key German manufacturing facilities, procure Germany's missile technology, and capture the V-2's launching sites. Von Braun and over 100 key V-2 personnel surrendered to the Americans, and many of the original V-2 team ended up working at the Redstone Arsenal. The US also captured enough V-2 hardware to build approximately 80 of the missiles. The Soviets gained possession of the V-2 manufacturing facilities after the war, re-established V-2 production, and moved it to the Soviet Union.