Perhaps the most unusual signal security procedure practiced during the war was the use of American Indians as "code-talkers." Because few non-Indians knew the difficult native languages, which in many cases had no written form, they provided ideal codes for relaying secret operational orders. In the European Theater several members of the Comanche tribe served as voice radio operators with the 4th Signal Company of the 4th Infantry Division. While the Army recruited only about fifty Native Americans for such special communication assignments, the Marines recruited several hundred Navajos for duty in the Pacific.
On the home front the United States government, as it had done during World War I, placed some restrictions upon broadcasting, including the closure of all amateur radio stations on 8 December 1941. The president created the Office of Censorship a few days later. It contained a cable division operated by Navy personnel to censor cable and radio communications, and a postal division operated by Army personnel to censor mail. The domestic press and radio operated under voluntary censorship guidelines, and on several occasions the press leaked the fact that the United States could read the enemy's codes. (Fortunately, the enemy was not paying attention.) Domestic commercial broadcasting, meanwhile, continued with minimal disruption.59 Unlike during the nation's two preceding wars, the international undersea cables were never cut. Despite fears that the enemy was using them to gain information, investigations after the war found no evidence that this had been the case.
During World War II signal intelligence and security assumed critical importance, and the efforts of the Army's intelligence specialists undoubtedly contributed to bringing the war to a speedier conclusion than would have otherwise been possible. Improvements in the handling and dissemination of signal intelligence had, by 1945, helped remedy the deficiencies evident at the time of Pearl Harbor.