During the early 1940s, the United States was actively involved in the development of new cruisers specifically designed to fulfill air-defense missions. They were to have 12 dual-purpose 152 mm guns, a speed of 33 knots, and a thick armor deck to protect against aerial bombs. After the outbreak of World War II, engineers were no longer bound by treaty constraints, although the ships size was to remain within the limits of a light cruiser. The project never came to life, but its underlying concepts served as the basis for the subsequent design of the Worcester-class cruisers.