With the start of the Cold War, American and Soviet strategists confronted the same challenge--how to strike at the heart of an enemy quickly in the event of war. Both nations began to investigate means other than piloted aircraft to deliver bombs to distant targets.

 At first they drew on German weapons technology from World War II, but the V-1 unpiloted flying bomb was too slow and vulnerable to enemy defenses, and the V-2 rocket was limited in both accuracy and range. Technological improvements gradually transformed the V-1 into the modern long-range cruise missile and the V-2 into the intercontinental ballistic missile (ICBM).

 Traveling at least five times faster than sound (hypersonic speed) and independent of signals from the ground, the ICBM seemed to be the "ultimate weapon."

CRUISE MISSILES: FLYING BOMBS

With rocket technology in its infancy, the United States and the Soviet Union initially turned to another technology for the ability to strike a distant enemy: an unpiloted flying bomb, today called a cruise missile. A cruise missile has wings and an air-breathing engine; so, unlike a rocket, it cannot operate outside the atmosphere. Unlike a piloted aircraft, a cruise missile uses an onboard automatic navigation system to guide it to the target.

V-1

The German V-1, introduced in combat in June 1944, was the world's first operational cruise missile. Thousands of pulse-jet powered V-1s, also known as "buzz bombs," were launched against cities in Europe. V-1s were slow and inaccurate; they could be intercepted and shot down.

Transferred from the U.S. Air Force