Nuclear weapon free zones (NWFZs) were an important development in the history of nuclear nonproliferation efforts. From 1957 through 1968, when the Treaty of Tlatelolco was signed, the United States struggled to develop a policy toward NWFZs in response to efforts around the world to create these zones, including in Europe, Africa, Latin America, and the Middle East. Many within the U.S. government initially rejected the idea of NWFZs, viewing them as a threat to U.S. nuclear strategy. However, over time, a preponderance of officials came to see the zones as advantageous, at least in certain areas of the world, particularly Latin America. Still, U.S. policy pertaining to this issue remained conservative and reactive, reflecting the generally higher priority given to security policy than to nuclear nonproliferation.