The V-2 (Vergeltungswaffe 2, Vengeance Weapon 2), manufactured by (at?) Mittelwerk as the Aggregat-4 (A4), was the first operational liquid-fueled ballistic missile. British propaganda attempts to attribute early V-2 strikes as gas-main explosions earned it the sarcastic nickname "the flying gas pipe." It was known in other circles as "the flying telephone pole," probably in reference to its vertical launch or the 9:1 fineness ratio, which probably looked longer and skinnier when it was glimpsed just before impact at Mach 4.

While a good deal was known about the V-2 during the war, from inspection of wreckage, no intact specimens were available for study before the end of the War in Europe. Willy Ley's evaluation in February, 1945, was based on British estimates and Goddard's theoretical models.