The Battle-class trawlers were Canada's response to Admiralty warnings about German U-boats threatening merchant shipping in the western Atlantic. Modeled on North Sea trawlers -- since standard Canadian fishing vessels were deemed unsuitable for patrol work -- the design produced a 130-foot vessel with a 25-foot beam, a 13-foot draught, and a top speed of 10 knots. Their main armament, a QF 12-pounder gun, was considered the smallest weapon that stood a chance of disabling a surfaced submarine. They also carried depth charges. Built on the Great Lakes and Saint Lawrence River at a cost of roughly $191,000 each, the trawlers were named after battles of the Western Front. Construction ran long, and the ships entered service late in the war. Thiepval barely saw combat before the Armistice.

Transferred to Canada's west coast after the war, Thiepval settled into a career that was far more varied than her designers had imagined. She conducted search and rescue patrols, enforced fisheries regulations -- sometimes seizing American boats caught in Canadian waters -- and carried out seal counts as part of the North Pacific Fur Seal Convention of 1911. On at least one occasion, she intercepted rum-runners near the Alaska border. The work was unglamorous but essential: a small navy ship holding the line on sovereignty, wildlife management, and Prohibition-era law enforcement simultaneously. She struck rocks twice in her early west coast years, near Prince Rupert in 1920 and in Gunboat Passage near Bella Bella in 1921, escaping both times with relatively minor damage. The rocks were patient.

In 1924, Thiepval embarked on her most dramatic mission: supporting a round-the-world flight attempt across the North Pacific. After waiting in Hakodate, Japan, she steamed to Petropavlovsk in the Soviet Union to meet the aircraft and crew. Bad weather delayed the flight until August 4, when the plane departed for its next leg. Heavy fog forced an emergency landing at sea, and waves badly damaged the aircraft before it came ashore at Nikolskoye on Bering Island. Thiepval steamed through the night, rescued the flyers, and salvaged the wreckage of their plane before making the long voyage back to Vancouver. It was the kind of mission that would define a ship's reputation -- a trawler designed for submarine hunting, threading through fog in Soviet waters to save aviators from a wrecked plane on a remote island.

After the Pacific rescue, Thiepval returned to routine duties. In 1925 she assisted the trawler Armentieres, which had struck a rock in Pipestem Inlet in Barkley Sound. The following year she towed the Mexican schooner Chapultepec off the rocks at Carmanah Point. Then, in 1930, her luck with rocks finally ran out. Thiepval struck a submerged rock in Barkley Sound and sank, coming to rest on the bottom with her armament still aboard. The wreck became a popular dive site, though its unexploded munitions gave it an edge that most recreational sites lack. Reports of ordnance visible to divers prompted the Department of National Defence to survey the site in 2011, and in 2017 Royal Canadian Navy clearance divers removed and disposed of the remaining shells. The trawler that survived U-boats, fog, Soviet waters, and rum-runners was finally made safe -- eighty-seven years after the sea claimed her.