The Castle Class Corvette HMCS ARNPRIOR was laid down in the yards of Harland and Wolff, Belfast, and launched on 8 February 1944. Intended for the Royal Navy and to be named Rising Castle, she was transferred to Canada and commissioned in her Navy on 8 June 1944. The ship was named in honour of Arnprior, a town in Renfrew County, Ontario, 42 miles west of Ottawa, at the confluence of the Ottawa and Madawaska Rivers.
After “working-up” exercises at Tobermory, Scotland, ARNPRIOR joined the Mid-Ocean Escort Force Group C-1 in August, working with it until the end of the war as a convoy escort between Londonderry, Northern Ireland, and St. John’s, Newfoundland.
Because of the torpedoing of HMCS CHEBOGUE, ONS-33 was one of her more memorable convoys. She left Londonderry on 30 September 1944 to join it. On 4 October, while engaging the German submarine U-1227 800 miles west of the United Kingdom, CHEBOGUE was struck in the stern by a GNAT or acoustic torpedo. ARNPRIOR and HMCS GIFFARD came to her aid. They took aboard a part of CHEBOGUE’s ship’s company, leaving others to work her when she should be taken in tow. Two men had been killed outright and four more died of wounds the following day.
CHEBOGUE was towed by various ships, finally by an ocean tug. She was brought in to Port Talbot, Wales. But her career was finished. She never returned to service and was paid off in September 1945.
After the end of hostilities in the Atlantic in May 1945, ARNPRIOR and her group made their farewells to Londonderry and left the Foyle to call at Greenock, Scotland, to embark for Canada personnel from HMCS NIOBE, the RCN establishment outside the town. They then sailed for home.
A refit followed from 8 June to 20 August 1945. On the 23rd of the latter month, ARNPRIOR was transferred from the Newfoundland Force to come under the administration of Captain “D”, Halifax. She landed stores and ammunition at Shelburne and Sydney, but was sent to sea again on 29 November, when the former HMCS MERRITTONIA went adrift while on tow to be delivered to her new owner. ARNPRIOR sailed with the CNAV BIRCHTON, tug, to West Jeddore, east of Halifax. But the seas were too heavy to effect a rescue. The battered ship grounded in Herring Cove and broke in two less than five hours later.
On 4 February 1946, ARNPRIOR was again ordered to go to the aid of a ship in distress, on this occasion, the SS Santa Marta. She was to stand by this ship until the U.S. Fleet Tug Paiute arrived to take her in tow. On the 7th, she accompanied the tug and tow back to Halifax.
However, like other ships in the immediate post-war Navy, she suffered from a manning shortage and had to be paid off along with most of the other corvettes. She made her farewell to the fleet on 14 March 1946. In the following June, she was purchased by Louis Levine of Montreal. Later, she passed into the hands of A. Gordon and Sons of Lunenburg. In 1951, she was bought by the Uruguayan government and towed to Halifax for a refit to prepare for her transfer. On 14 June 1953, she was commissioned into the Uruguayan Navy as Montevideo. Montevideo would carry out her duties as a training vessel until 1975.