The Radio Act of 1912 gave the president legal permission to shut down radio stations "in time of war", and during the first two and a half years of World War I, before US entry, President Wilson tasked the US Navy with monitoring US radio stations, nominally to "ensure neutrality." The navy used this authority to shut down amateur radio in the western part of the US (the US was divided into two civilian radio "districts" with corresponding call-signs, beginning with "K" in the west and "W" in the east, in the regulatory measures; the navy was assigned call-signs beginning with "N"). When Wilson declared war on Germany on April 6, 1917, he also issued an executive order closing most radio stations not needed by the US government.