During the late 1990s, the U.S. Navy realized its Cold War-era cruisers and destroyers had been designed for open-ocean warfare, and would be vulnerable in shallow coastal waters, where they would face dangers from high-speed boats, missile-firing fast-attack craft, small submarines, sea mines, and land and air-launched anti-ship missiles. The Navy's official solution was the DD-21, a large coastal warship that could absorb hits. Two Navy strategists, retired Captain Wayne Hughes and Vice Admiral Art Cebrowski, refined an opposing "Streetfighter" concept for a 1,000-ton small, specialized, and heavily armed vessel costing just $90 million (2001 dollars). Being small, light and numerous, the Streetfighter was envisioned as a "single-serving" ship to be abandoned once hit, made possible by its low cost. The concept of a manned expendable warship was contentious and the idea was not picked up. When Donald Rumsfeld was made Secretary of Defense in early 2001, he promised transformational approaches and doing jobs with fewer people. In October 2001, Cebrowski was assigned to head the Pentagon's new Office of Force Transformation, shortly after which Admiral Vernon Clark cancelled the DD-21 and replaced it with a "family" of ships, including the littoral combat ship, being motivated to produce ships cheaper and faster to increase fleet size. Clark declared the LCS was his "most transformational effort" and number-one budget priority in 2003.