Her task was to act as part of the radar defenses of the United States in the Cold War, serving until 1965.

Guardian (YAGR-1) was laid down on 20 March 1945, under a United States Maritime Commission (MARCOM) contract, MC hull 3137, as the Liberty Ship James G. Squires, by J.A.

[5][4] The first ocean radar station ship put into service by the Navy, Guardian conducted shakedown in Roosevelt Roads, Puerto Rico, and surrounding waters, reporting to Newport, Rhode Island, her home port, 2 June 1955.

[5] In addition to radar picket duty, Guardian participated in ASW exercises with both American and Canadian naval units and in local operations out of Newport and Key West, Florida.

She was returned to the United States Maritime Commission (MARCOM) for lay up in the National Defense Reserve Fleet.