Upon entry into the service, he went to the Coast Artillery Officers Candidate School.

Lieutenant Pinnick was then made a Coast Artillery Unit Commander.

He was responsible for proper fire control. John also had the administrative duties of the battery. He was also responsible for the training and discipline of the enlisted personnel.

He was assigned as an Operations and Training Staff Officer for 12 months. Following that, he was assigned as a Coast Guard Unit Commander.

Lt Pinnick was assigned to numerous posts in the Pacific theater including New Guinea and Korea as well as several posts in the USA.

Lt. Pinnick awards included: the American Theater ribbon, Asiatic-Pacific Theater Ribbon, WW II Victory Medal, and the Occupation of Japan Medal.