During July 1943, Protector was requisitioned for war service by the U.S. Army. On the way to New Guinea and off Gladstone, she was damaged in a collision with a tug and abandoned. The hull was subsequently taken to Heron Island off the Queensland coast and later sunk for use as a breakwater. Her rusting remains are still visible to this day.
Built at William Armstrong & Co, Newcastle on Tyne, England, Protector was built to a standard type F1 flat-iron gunboat design, but was one of the largest of its type, and was classified as a light cruiser, with a displacement of 920 tons. Her length was 180 feet 6 inches (55.02 m), with two compound surface-condensing engines that produced 1,500 horsepower (1,100 kW). Her top speed was 14 knots (26 km/h; 16 mph). To conserve fuel (coal) she was also originally rigged as a topsail schooner.
For her size, Protector was exceptionally heavily armed. Her largest weapon was the 8-inch (203 mm) Armstrong-rifled breech-loading gun mounted at the bow. The gun weighed 12 tons and could fire a 180-pound (82 kg) shell 7,500 yards (6,900 m) using a charge of 90 lb (41 kg) of black powder.
Other armaments included five 6-inch (152 mm) Woolwich-Armstrong rifled breech-loading guns; four 3-pounder 1.85-calibre Hotchkiss QF guns and five 10-barrel (1.6 m3) Gatling machine guns. Her small arms consisted of 200 0.45 Martini-Henry rifles Mk IV, 100 breech-loading revolvers, 100 cutlasses and 30 boarding pikes.
At the outbreak of World War I, her armament was increased to include two 4-inch (100 mm) guns, two 12-pounder guns and four 3-pounder guns.