After World War II ended, the U.S. Navy entered the 45 year long Cold War and participated in the Korean War, the Vietnam War, the First Persian Gulf War, and the &lt;a href="Iraq%20War"&gt;Second Persian Gulf War / Iraq War&lt;/a&gt;. Following the collapse of the Soviet Union in 1990–91, the Soviet Red Navy fell apart, which made the United States the world's undisputed naval superpower. Nuclear power and ballistic missile technology led to new ship propulsion and weapon systems, which were used in the s and s. By 1978, the number of ships had dwindled to less than 400, many of which were from World War II, which prompted Ronald Reagan to institute a program for a modern, 600-ship Navy. Today, the United States is the world's undisputed naval superpower, with the ability to engage and project power in two simultaneous limited wars along separate fronts.