Commodore John Tobin joined the Royal New Zealand Navy in 1951 and was immediately sent to the United Kingdom to train at the shore establishment HMS BRITANNIA, the Royal Naval College and the training cruiser HMS DEVONSHIRE. On promotion to Midshipman he was posted to the Southampton class cruiser HMS BIRMINGHAM and experienced war service in Korea.
On return to New Zealand in 1955 Tobin served briefly in the training ship HMNZS KIWI and in the shore establishment HMNZS PHILOMEL before joining the cruiser HMNZS ROYALIST in 1957. After six months in HMNZS ROYALIST as watchkeeper, he was posted to the wireless transmitting station HMNZS IRIRANGI at Waiouru as Transport Officer.
In mid 1959 Tobin undertook a two year exchange with the Royal Navy which included time training as an Air Direction Officer. He completed his exchange time in the aircraft carrier HMS ARK ROYAL.
John Tobin returned to New Zealand in late 1961, serving for a little over a year in the shore establishment HMNZS WAKEFIELD before joining the New Zealand High Commission in Singapore as Defence Liaison Officer. He returned to New Zealand in mid 1966 and took up the post of Operations Officer in the frigate HMNZS WAIKATO, followed a year later by service in the frigate HMNZS OTAGO as Executive Officer. Additional service as Project Officer of the frigate HMNZS CANTERBURY was followed by Tobin taking command of HMNZS WAIKATO in late 1973.
John Tobin came ashore in 1975, serving on the staff at HMNZS PHILOMEL in a variety of postings including the position of Director Naval Operations and Plans later that same year.
In late 1979 Tobin was sent back to the United Kingdom to take up the position of Deputy Head of Liaison, within a year becoming Head of New Zealand Defence Staff Liaison. Tobin returned to New Zealand in early 1984 and became Commanding Officer and Captain Fleet Support at HMNZS PHILOMEL.
John Tobin retired from the RNZN in December of 1985 having attained the rank of Commodore.