In 1942, when the U.S. Navy was desperately short of antisubmarine assets, “Reverse Lend Lease” was arranged with Great Britain to provide 25 “Flower” and “Modified Flower”-class corvettes to help combat the U-boat menace in the Atlantic. The first ten, numbered as gunboats PG-62-71, were standard “Flowers” that already had seen some service in the Royal Navy. The other 15 (PG-86-100) were “Modified Flowers” still under construction in Canada, and seven were reallocated to the Royal Navy prior to delivery (PG-88, 90, 91, and 97-100). All were powered by a single vertical triple-expansion reciprocating steam engine with steam supplied by two boilers; maximum speed was a modest 16.5 knots. Crews consisted of five to seven officers and 82 enlisted personnel. All of the ships survived the war.
The Tenacity (PG-71) is pictured at top right in June 1942, three months after commissioning and still lacking radar. In all the U.S. Navy’s standard “Flowers,” an old U.S. 4-inch Mk 12 gun was substituted for the shielded British gun of the same bore, while a 3-inch Mk 22 mount replaced the British 2-pounder “pom-pom” gun aft. Only two 20-mm cannon were fitted initially to defend against aircraft, and antisubmarine armament was limited to two depth-charge racks. Later, all U.S. Navy units of both groups carried four 20-mm guns, a fixed Hedgehog spigot mortar mounted to starboard and just abaft of the forecastle gun, four Mk 6 K-gun depth-charge mortars, and the two depth charge racks, with augmented stowage.
The Surprise (PG-63) is pictured in May 1944, after the addition of the Hedgehog, a tripod mast to support an SO-series surface-search radar, and the full suite of depth-charge launchers. Launched on 5 June 1940, as HMS Heliotrope, she was commissioned into the U.S. Navy on 24 March 1942. Prior to being handed back to the British in August 1945, she had escorted convoys in the Caribbean, South Atlantic, and North Atlantic in a wartime career typical of her type. After a brief mercantile career, the ship fell into Chinese Communist hands, serving in their navy until the 1970s.
The 1,375-ton, Canadian-built Prudent (PG-96), like all U.S. Navy “Modified Flowers,” was armed with two 3-inch 50-caliber Mk 22 dual-purpose guns, with the forward mount on a platform raised well above the forecastle level. All eight were delivered with bulky British Type 271 lantern-type surface- search radars (later replaced by mast- mounted SO-series sets) on pedestals at the after end of the bridge, which itself was considerably higher than on the earlier “Flowers.” The “Modified Flowers” also had increased hull flare and freeboard forward to improve seaworthiness. The Prudent, begun as HMS Privet, was commissioned on 16 August 1943 as the last U.S. Navy corvette. Decommissioned in October 1945, she was transferred to Italy in 1949 and later converted into a survey ship.