There is a paradoxical quality to international science after 1940. World War II and the Cold War restricted many traditional avenues of scientific internationalism: atomic physics and allied fields became shrouded in national security restrictions; basic data (including sea floor soundings and geodetic data) were restricted or classified; and communications between Western and Soviet scientists frayed. Espionage agencies recruited scientists, international scientific meetings were postponed or delayed, and the universalist practices of science were attacked as unpatriotic and dangerous within leading scientific nations.