In 1944 the Germans began to use two new pilotless weapons against targets in the UK.
The V1 Flying bomb, also known as a Doodlebug because of the sound made by its engine, was a similar concept to today's Cruise missile. A V1 was launched from the ground and continued in level flight until it ran out of fuel (hopefully over its intended target). After gliding to the ground it exploded like a conventional bomb.
V1's were responsible for killing over 6,000 people and seriously injuring over 17,000 more. The first V1 fell on London during the night of 13th June 1944, shortly after D-Day, by 18th June over 500 had been launched. This came as a great shock to the people of London. Allied Intelligence however had known about the V1 for a long time. If not for the efforts of the Allied air forces, that had been waging a secret war against the launch facilities for over a year, the first attack may have been around 6 months earlier.
Defense against this weapon was similar to that against any manned bomber except that the V1, at 640 kph (400 mph), was much faster than previous bombers and it took a very determined pilot in a fast fighter to deal with it. As well as fighters anti-aircraft guns and barrage balloons were used to great effect. All told only about one quarter of the 10,000 or so V1's launched managed to reach their targets causing a great deal of death and destruction.
By the end of August 1944 Allied ground forces had overrun the launch sites in France and the number of V1 attacks dwindled. In October the V1's began to be launched from aircraft and attacks continued from then on until March 1945.
The V2 Rocket was a Ballistic Missile fired vertically into the atmosphere that came back down to Earth at the speed of sound due to gravity.
The only defense against such a weapon was to destroy it on the ground before it could be launched, or to destroy its launch installations and the manufacturing plant that produced it.
The first V2 landed on London during the evening of 8th September 1944. Between then and late March 1945 over 1,400 V2's were launched at London.
Whereas the V1 could be heard approaching the only warning that a V2 gave was the sonic boom shortly before impact. It was a terrifying weapon that was responsible for killing nearly 3,000 British civilians and injuring over 6,500 more.
After the war there was a race by the Americans and Russians to obtain the V2 technology and the engineers responsible for designing and producing it. V2 technology was used to develop post war ballistic nuclear missiles and the rockets that have since allowed men to travel in space and to the Moon and back.