In 1937, with the Nazis in power, he joined the S.S.. Von Braun worked in Peenemünde between 1937 and 1945. There, he started to develop a new rocket called A4 (Aggregat 4). After some tests, the rocket was renamed to V-2. The "V" is for the German word "Vergeltung", which means revenge. This was the first long range ballistic missile to be used in war. It was able to carry a one ton warhead up to 50 miles into the air, and travel hundreds of miles to a target. In 1943, Germany started a mass production of this rocket using thousands of concentration camp prisoners as factory workers. They fired thousands of these rockets at targets in Antwerp and Great Britain, especially London. More than 1700 V-2 rockets landed on Antwerp, killing more than 3,700 people. Von Braun and his team started to develop the new generations of these rockets, the V-9 and V-10, which were for targets in the US.