Short answers, pulled from the story.
The V-2 rocket, formally named the Vergeltungswaffe 2 and developed as the Aggregat-4, was the world's first practical, modern ballistic missile. Nazi Germany developed it as a vengeance weapon during World War II and used it to attack Allied cities, primarily London and Antwerp, beginning in September 1944. More than 3,000 were launched before the war ended.
The V-2 was developed primarily by Wernher von Braun and Walter Dornberger at the Peenemünde Army Research Center. Dr. Walter Thiel designed the 25 ton rocket motor, and Helmut Hölzer developed the Mischgerät analog computer used for guidance. Von Braun's doctoral thesis on liquid propellant rockets, classified by the German Army in 1934, was a foundational document in the program.
The first V-2 attack on London occurred on the 8th of September 1944, when a rocket launched from The Hague struck Staveley Road, Chiswick, killing three people: Ada Harrison aged 63, Rosemary Clarke aged three, and Sapper Bernard Browning of the Royal Engineers. Earlier that same day, a single rocket had been fired at Paris, causing modest damage near Porte d'Italie.
According to a 2011 BBC documentary, V-2 attacks killed an estimated 9,000 civilians and military personnel. In London alone, an estimated 2,754 civilians were killed and another 6,523 injured. The single deadliest V-2 strike was on the 16th of December 1944, when a rocket hit the Cine Rex cinema in Antwerp, killing 567 people and injuring 291.
After 100 km was selected to define the edge of space, the V-2 retroactively became the first artificial object to travel into space. This occurred during the vertical launch of test rocket MW 18014 on the 20th of June 1944, which reached a peak altitude of 174.6 km, the highest altitude reached by any V-2 during the war.
The United States, Soviet Union, France, and United Kingdom all competed to capture V-2 hardware and personnel after the war. The U.S. acquired 300 rail-car loads of V-2 components and recruited 126 principal designers through Operation Paperclip, including von Braun and Dornberger. The Soviet Union had German engineers rebuild and launch V-2s, leading eventually to the R-7 rocket that launched Sputnik 1 in November 1957. France redirected its V-2 research into the Véronique sounding rocket and ultimately the Ariane rocket family.