The Minuteman nuclear intercontinental ballistic missile transformed the United States' strategic nuclear capability by replacing liquid-fueled missiles that had serious safety concerns, required massive support facilities, and responded slowly. As a solid-fueled missile, the Minuteman could remain safely and constantly on alert in an isolated Launch Facility like November-33 and be launched almost instantaneously. Its smaller size, greater safety, and lower cost allowed the U.S. nuclear arsenal to expand rapidly, and between 1962 and 1967 the U.S. developed and deployed 1,000 operational Minuteman missiles. Its speed and reliability earned it the nickname America's "Ace in the Hole." In 1965, the first Minuteman missiles were activated in the missile field of the 321st Strategic Missile Wing, the first wing to receive the Minuteman II, and by the end of 1966 the wing had 150 operational Minuteman II missiles, including one housed at November-33. The Minuteman II improved on the Minuteman I with greater accuracy from an improved guidance system, a longer range increased from 6,300 miles to 7,000 miles by improved boosters, and a greater payload capacity with the W56 warhead, which had a yield of 1.2 megatons. In 1970, the 321st Strategic Missile Wing's Minuteman II missiles were replaced by Minuteman III missiles, which introduced a new re-entry system and could carry up to three Multiple Independently Targeted Re-entry Vehicles, allowing a single missile to strike three separate targets. Although the Minuteman III's W62 warhead had a lower explosive yield of approximately 170 kilotons than the Minuteman II's single warhead, the missile could travel at a top speed of 15,000 mph for a distance of 8,000 miles and reach those targets quickly. In response to the Strategic Arms Reduction Treaty of 1991, the 321st Strategic Missile Wing was deactivated on July 2, 1998, its Minuteman III missiles were removed from their silos, and the silos were imploded. Even so, 450 fully operational Minuteman III missiles remain among three Air Force Based: Minot AFB in Minot, North Dakota, F.E. Warren AFB in Cheyenne, Wyoming, and Malmstrom AFB in Great Falls, Montana.