The 'Raids on Nauru' were a pair of German attacks on the phosphate-rich small island of Nauru in the central part of the Pacific Ocean (6/8 and 27 December 1940).

Possessing an area of only 8.1 sq miles (21 km²), Nauru is an island in the Micronesia subregion of Oceania, and is a blunt-ended essentially oval-shaped island in the south-western Pacific Ocean, 34.8 miles (56 km) to the south of the equator. The island is almost wholly surrounded by a coral reef, which is exposed at low tide and dotted with pinnacles, and whose presence prevented the establishment of a port, although channels in the reef allow small boats access to the island. A coastal strip, 490 to 985 ft (150 to 300 m), wide lies inland of the beach: this is the island’s only fertile area, in which coconut palms flourish, and the area round Coral cliffs surround Nauru’s central plateau, and the plateau’s highest point, Command Ridge, is 233 ft (71 m) above sea level. The only fertile areas on Nauru are the narrow coastal belt, where coconut palms flourish, and the land around Buada Lagoon, where bananas, pineapples, vegetables, pandanus trees and indigenous hardwoods, such as the tamanu tree, grow.

Nauru was one of three great phosphate rock islands in the Pacific Ocean, along with Ocean island (now Banaba) in the Gilbert islands group (now Kiribati) and Makatea in the Tuamoto islands group of French Polynesia.

The German attacks were conducted by auxiliary cruisers between 6 and 8 December and on 27 December. The raiders sank five Allied merchant ships and inflicted serious damage on Nauru’s economically important phosphate-loading facilities. Despite the significance of the island to the Australian and New Zealand economies, Nauru was not defended, and the German force suffered no losses.

The two attacks were the most effective operations conducted by German raiders in the Pacific Ocean during World War II. They disrupted supplies of phosphate to Australia, New Zealand and Japan, which reduced agricultural production in these countries. In response, Allied naval vessels were deployed to protect Nauru and nearby Ocean island and to escort shipping in the South Pacific, and small garrisons were also established to protect the two islands.

Nauru and Ocean islands were important sources of phosphate for Australian and New Zealand fertiliser production and thus played an important role on both countries' agriculture industries at the time of World War II. The Melbourne-based British Phosphate Commission (BPC) managed the extraction and export of phosphate from the islands and dominated all aspects of Nauruan life. During the year ending 30 June 1940, the BPC shipped almost one million tons of phosphate from Nauru and about half that amount from Ocean island using its fleet of four vessels (Triadic, Triaster, Triona and Trienza) as well as chartered merchant vessels. As the islands have no harbours or anchorages, the phosphate ships were loaded by securing to deep moorings and embarking their cargo via cantilever jetties. During periods of south-westerly winds, which are common from November to March, the ships had to stop loading and move away from the island until conditions improved. It was common for these ships to be allowed to drift to save fuel, and there were often several vessels lying off Nauru.

Despite their importance to the Australian and New Zealand economies, Nauru and Ocean islands had been allocated only a low priority for the limited military assets available to protect the Australia Station, and as a result both islands were undefended in December 1940. Strategic stockpiles of phosphate had been built up in Australia, however, to lessen the impact of any interruption on the supply of phosphate.

Late in October 1940, the German raider Orion, commanded by Kapitän Kurt Weyher, met Komet, commanded by Kapitän Robert Eyssen, as well as the supply ship Kulmerland, at Lamotrek in the Caroline islands group. As the more senior of the two captains, Eyssen then assumed overall command of the force. The three ships operated off New Zealand’s eastern coast for 18 days during November, sinking the small coaster Holmwood and the 16,712-ton ocean liner Rangitane with gunfire on 25 and 27 November respectively, without being detected by the weak New Zealand defence forces. After these attacks, the raiders shifted to the Kermadec islands group, and here transferred their female and child prisoners to Kulmerland on 29 November. The three ships then proceeded to Nauru to attack the island’s phosphate industry and the concentration of shipping which the German captains knew was usually present.

The German force encountered its first BPC ship while passaging to Nauru. On 6 December, the 4,413-ton Triona was attacked to the north-east of the Solomon islands group and sunk with torpedoes after a chase in which three of her crew were killed by the raiders' guns. All 68 survivors were taken prisoner.

The raider captains intended to land a shore party and also to shell Nauru’s shore installations at dawn on 8 December, but bad weather forced them to concentrate on the ships which were off the island. On the evening of 7 December Komet, which had gone ahead to reconnoitre and was disguised as the Japanese merchant ship Manyo Maru, sank the 5,181-ton Norwegian merchant vessel Vinni at a point about 9 miles (14 km) to the south of Nauru. The raider was spotted from the shore, but her disguise was successful and she was assumed to be a merchant ship bound for Japan.

Orion joined Komet off Nauru in the early hours of 8 December, and attacked and damaged the 6,378-ton Triadic and and sank the 6,032-ton Triaster. Komet then tried unsuccessfully to sink Triadic with scuttling charges, so Orion sank the merchant vessel with gunfire. Komet later sank the 3,900-ton British steamer Komata. Following these attacks, the two raiders and Kulmerland withdrew to regroup 20 miles (32 km) to the east of Nauru. As the weather precluded a landing on the island, it was decided that Komet and Kulmerland would go to Ailinglaplap in the Marshall islands group, where Komet would refuel, while Orion operated to the north-west of Nauru. Following this, the ships would meet off the island and make another attempt to land a raiding party.

When the German force reassembled off Nauru on 15 December, the weather was still too bad to permit a landing, and the attack on Nauru was broken off. Further attacks on shipping were judged impractical, as the raiders had intercepted radio messages ordering vessels bound for Nauru and Ocean islands to disperse. Instead, the three German ships proceeded to the Australian-administered island of Emirau in the Bismarck islands archipelago to land the 675 prisoners they were carrying. Weyher refused to release any of the European prisoners on board Orion as he believed that 'trained officers and crews are as much a problem for Britain as shipping itself', but the ships landed 343 Europeans and 171 Chinese and South Pacific people.

Fortunately for the Germans, Emirau was one of the few islands in the region without a radio of the type supplied by the Australian navy with which to contact the Australian authorities. The island’s two European families provided the released prisoners with supplies, and sent a canoe to Kavieng in New Ireland to notify the Australian colonial government. A schooner was dispatched to bring additional supplies to Emirau, where it arrived on 24 December. The colonial administrator of New Britain and further supplies was also flown to Emirau on board a flying boat. The released prisoners were embarked onto the steamer Nellore on 29 December for movement to Townsville in Queensland, where they arrived on 1 January 1941. They provided useful intelligence on the German raiders' operations, and the German naval staff issued a directive on 19 February 1941 prohibiting raiders from releasing further prisoners.

The three German ships parted company after departing Emirau on 21 December. Orion proceeded to Lamutrik and then Maug in the northern part of the Mariana islands group to overhaul her engines, Kulmerland went to Japan, and only Komet continued operations in the South Pacific. She attempted to lay mines off Rabaul on 24 December using her motor boat, but this project was abandoned when the boat’s engines failed. Komet then returned to Nauru, which she reached at 05.45 on the morning of 27 December. After issuing a warning for those on shore to not use radio and signalling her intent to destroy the phosphate loading plant, she opened fire at 06.40. The bombardment lasted for about one hour, during which time the raider wrecked the loading plant, oil tanks, boats, buildings and mooring buoys. Following this attack, she sailed to the south-east and Nauru broadcast news of the attack to Australia. This was the last visit of German ships to Nauru during the war, and Komet now transferred her activities to the Indian Ocean.

The German raids on Nauru adversely affected the Australian and New Zealand economies, and were arguably the greatest success achieved by German raiders in the Pacific Ocean during World War II. It was 10 weeks before phosphate export could be resumed from Nauru, and the loss of ships and damaged infrastructure led to a significant decline in output. The resulting phosphate shortages forced the introduction of fertiliser rationing in New Zealand from July 1941. Komet's bombardment of the island also interfered with phosphate consignments to Japan, which caused the Japanese government to threaten to reduce the aid it was providing to Germany. The success of the attacks on Nauru led to rumours in Australia and New Zealand that the raiders had been aided by treachery in the islands. Several investigations were conducted into the rumours and proved them to be unfounded.

Following the raids, the commonwealth military forces in the Pacific took steps to prevent further attacks by raiders. The Royal Australian Air Force and Royal New Zealand Air Force flew an increased number of patrols in search of raiders operating near major ports. In addition, the Australian Naval Board requested that the British Admiralty authorise the redeployment of Australian naval units to meet the threat posed by raiders: this was agreed, and the light cruiser Sydney and armed merchant cruiser Kanimbla returned to Australia from other stations. This allowed the provision of naval protection to Nauru and Ocean islands, and the armed merchant cruiser Manoora arrived off Ocean island on 4 January 1941 escorting Trienza. Several Australian and New Zealand warships maintained a continual presence off the islands during subsequent months, and two field guns were deployed to each island. The attacks also led to the introduction of convoys between Australia and New Zealand. The naval authorities were able to exploit the intelligence gained from the prisoners landed at Emirau to reroute merchant ships away from the areas in which the German raiders were operating. This greatly reduced the raiders' effectiveness, and Komet and Orion sank only three more ships in the period between the attack on Nauru and their return to Europe late in 1941.

After the German had sunk the five Australian ships off the island on 6 December 1940, the Japanese bombed the island on 9 December 1941. The remaining Europeans were evacuated in February 1942, and elements of the 43^rd Guard Force occupied the island on 25 August 1942. An airfield was constructed on the southern coastal strip by March 1942, and at its peak this two-runway facility was protected by as many as 200 anti-aircraft guns. Following the 'Raid on Makin', the garrison was reinforced to a strength of about 3,700 troops, and about 1,200 members of the local population were forcibly relocated to Truk, where one-third of them died.

The Allies made plans to invade Nauru at the same time as the 'Longsuit' assault on Tarawa, but when senior commanders saw models of the island’s topography, the invasion was sensibly cancelled and Makin was substituted.

On 4 December 1943, a US force of two carriers, five battleships and 12 destroyers, under the command of Vice Admiral Willis A. Lee, the commander Battleships, Pacific Fleet, raided the island in an attempt to catch and destroy a large force of Mitsubishi G4M 'Betty' twin-engine medium bombers which had retired there from Kwajalein. However, the US attacks were too late to find many targets: perhaps eight Japanese aircraft were destroyed at the cost of four US aircraft destroyed and one destroyer damaged.