During the 1950s and 1960s, elaborate computerized early warning systems such as Defense Support Program were developed to detect incoming Soviet attacks and to coordinate response strategies. During this same period, intercontinental ballistic missile (ICBM) systems were developed that could deliver a nuclear payload across vast distances, allowing the U.S. to house nuclear forces capable of hitting the Soviet Union in the American Midwest. Shorter-range weapons, including small tactical weapons, were fielded in Europe as well, including nuclear artillery and man-portable Special Atomic Demolition Munition. The development of submarine-launched ballistic missile systems allowed for hidden nuclear submarines to covertly launch missiles at distant targets as well, making it virtually impossible for the Soviet Union to successfully launch a first strike attack against the United States without receiving a deadly response.