 However, with the entrance of the United States into World War One in April 1917, all civilian stations were ordered to cease operations, and the University's radio station was shut down for the duration of the conflict.During the war, the college trained over 300 radio operators for the United States Army.With the end of the war and the subsequent re-establishment of civilian radio, in August 1920 the University was again issued a "Technical and Training School" license, now with the call sign of 9YK.