Operation Mercantile

'Mercantile' was a US unrealised plan for an amphibious assault on the north-western end of the Japanese-occupied island of New Ireland leading to the capture of Kavieng, round which were centred some of the primary Japanese land, sea and air bases in the region (1944).

The plan was cancelled on 12 March 1944 after the Allies had reached the strategic decision to bypass the Rabaul area of New Britain and the whole of New Ireland, leaving the Japanese garrisons to 'wither on the vine' without outside support, but elements of the plan were nonetheless used when Allied forces arrived to occupy the island after the surrender of the Japanese in August 1945.

New Ireland is the second largest island in the Bismarck islands archipelago, about 200 miles (320 km) in length and between 8 and 20 miles (13 and 32 km) wide, with an area of 2,859 sq miles (7404 km˛). The island is located to the north of New Britain and to the north-west of the Solomon islands group, and shares the jungle terrain of both these other areas.

In 1941 the island was under Australian mandate, and there was a good but undeveloped anchorage at Kavieng on the north-western tip of the island, but this was overshadowed by the superb anchorage at Rabaul on the north-eastern tip of New Britain. Besides being jungle-clad, New Ireland is rugged and reaches a maximum height of 7,805 ft (2379 m). The central mountain ridge of the island’s south-western two-thirds drops steeply into the ocean along the south-west coast, but descends more gradually to the north-east, where there is a narrow coastal plain. The indigenous population numbered about 54,000 persons speaking more than 45 different dialects, and there were about 200 European residents.

Some 500 men of the 2nd Maizuru Special Naval Landing Force occupied Kavieng on 23 January 1942, whereupon the Australian garrison, which had just completed an airstrip, cratered its runway and retreated into the island’s interior. The Japanese garrison was later reinforced with men of the 14th Base Force, 5th Kure Special Naval Landing Force and 5th Sasebo Special Naval Landing Force.

The Japanese attempted to reinforce the garrison in December 1943, using the super-battleship Yamato to carry the troops, but the super-battleship was hit on 25 December 1943 by a torpedo from the US submarine Skate: this torpedo hit caused damage serious enough to force the cancellation of the reinforcement attempt.

Kavieng was hit hard from the air the same day as |Rear Admiral Frederick C. Sherman’s Task Group 50.2 raided the island with 86 aircraft and found the anchorage almost deserted. A weak counterattack that night by four Mitsubishi G4M 'Betty' medium bombers and seven Nakajima B5N 'Kate' light bomber failed to score any damage. There were further US raids in the next few weeks, including one on 1 January 1944 against a convoy returning from Rabaul to Truk that did little damage but drew off Japanese air strength during the 'Dexterity' landing at Saidor.

By this time the Japanese had constructed three more airstrips, one to the south of Kavieng, one at Namatani and one at Borpop.