The tragic sinking of the Montevideo Maru: Australia’s worst maritime disaster in history

Early in 1942, Japanese forces targeted the strategic harbour town of Rabaul on the island of New Britain, then part of the Australian-controlled Territory of Papua and New Guinea.

The town had served as the key base for Lark Force, which included the 2/22nd Battalion of the 23rd Brigade, 8th Division of the Second AIF, along with artillery and signals units, including local militia from the New Guinea Volunteer Rifles.

Japanese air raids began in early January, but the main invasion force landed on 23 January and quickly overran the outnumbered and underprepared garrison. 

Although a few managed to flee into the jungle, most personnel were captured and marched to prison camps around the town.

Among those detained were missionaries from the Missionaries of the Sacred Heart, plantation managers, wireless operators, business owners, and government staff, who had refused evacuation orders.

Japanese forces made little distinction between soldiers and civilians when selecting prisoners for internment.

Over the following months, disease, overcrowding, poor rations, and inadequate medical care made conditions in the camps, which were already poor, much worse. 

Eventually, Japanese authorities seem to have decided to move many of the prisoners to Hainan Island, which had become an important base for military operations further south.

The exact destination of the ship was never officially confirmed, though postwar investigations suggest that it was headed to Hainan via the Philippines.

To carry out this transfer, they chose the Montevideo Maru, a converted merchant ship that showed no Red Cross insignia or external markings to indicate it carried prisoners.

The guards received orders to keep all internees below deck and to prevent any form of communication or movement during the voyage.

The Montevideo Maru had been built in Nagasaki in 1926 by the Osaka Shosen Kaisha shipping line and originally operated as a commercial passenger vessel that operated on routes between Japan and Latin America.

Known in Japanese as モンテビデオ丸, it was taken over for wartime service after Japan entered the war.

The navy stripped it of identifying features and did not arm it for this voyage.

On 22 June 1942, Japanese guards began forcing prisoners aboard in Rabaul Harbour.

Those forced into the holds included 979 members of the Australian military and at least 81 civilians, most of whom had been held in the Rabaul camps for months.

Once confined inside the lower decks, the prisoners received almost no food or water.

The air became stifling, and no medical provisions had been arranged. Although the guards had limited contact with the prisoners, they remained alert for signs of resistance and refused to let anyone above deck. 

The ship proceeded northward without making any radio contact. For several days, it sailed across the Bismarck Sea and entered the South China Sea, and it stayed entirely undefended.

Just before 3:00 a.m. on 1 July, as it neared the Philippines, approximately 100 kilometres northwest of Cape Bojeador, when the USS Sturgeon detected its presence.

Without any knowledge of its cargo, Commander William L. Wright gave the order to fire torpedoes.

One of them struck near the engine room, which caused a power failure that plunged the ship into darkness. 

Almost immediately, the vessel began to list. Below deck, prisoners were trapped behind sealed hatches, with no ladders or access to exits.

Some guards attempted to reach lifeboats, but none opened the holds. There had been around 100 Japanese crew and guards aboard, and 88 of them survived the sinking.

Within minutes, the ship rolled and disappeared beneath the surface. All of the prisoners on board drowned.

At first, no one outside Japan knew what had occurred. The Sturgeon crew logged the attack as a successful strike on an enemy transport, unaware that they had killed over a thousand Allied personnel.

No signals or messages had warned of the ship’s contents. Japanese naval authorities made no effort to inform the International Red Cross or Allied governments of the loss.

The names of the dead had gone unrecorded in Allied war records for years. 

For Australian families, the absence of information created years of anguish. Some believed their relatives remained alive in secret camps.

Others received letters, written months earlier, that arrived after the ship had sunk.

As a result, many clung to the hope that their sons or brothers had survived. The Department of Defence had no access to Japanese records and could not confirm what had happened to the men captured at Rabaul. 

Only after the war ended did the truth begin to surface. In October 1945, Australian investigators discovered captured Japanese documents that mentioned the Montevideo Maru and its human cargo.

Investigators then put together the passenger list by comparing unit lists and other wartime records.

They verified the location and circumstances of the sinking. The revelation brought closure to at least some families, but it also caused fresh grief.

Families had spent over three years in a state of uncertainty, unaware that their loved ones had already died at sea.

Survivors from among the Japanese crew later confirmed that prisoners had remained locked below deck throughout the sinking, and their testimonies supported the documentary evidence. 

The tragedy later became part of the record in postwar investigations into Japanese war crimes, although no individual was prosecuted specifically for the incident.

For decades, the shipwreck’s location remained largely a mystery. Although historians and veterans’ organisations continued to research the incident, the depth and distance of the wreck from land made recovery impossible.

Over the years, commemorations were held and plaques were installed as communities erected memorials in towns such as Ballarat, where many of the 2/22nd Battalion and its regimental band had come from.

Each year, Ballarat hosts a special tribute that honours their memory through musical performance.

The Montevideo Maru is also formally recognised at the Australian War Memorial in Canberra, where a commemorative plaque and inscribed wall list the names of those who died.

However, no physical confirmation of the sinking existed, and doubts about the exact location persisted into the 21st century. 

Eventually, in April 2023, a deep-sea expedition led by the Silentworld Foundation and Fugro used sonar and unmanned autonomous underwater vehicles (AUVs) and discovered the wreck of the Montevideo Maru at a depth of over 4,000 metres in the South China Sea, approximately 110 kilometres northwest of Luzon.

Its identity was confirmed by its structure and layout, and this included damage in the region of the engine room.

Sonar scans and underwater photography revealed the hull split but largely intact, and no effort was made to disturb the site. 

After the discovery, Prime Minister Anthony Albanese acknowledged the significance of the find and paid tribute to those who had died.

Relatives of the victims, who had waited through generations of uncertainty, attended national commemorations, and the news gave some a sense of peace.

The rediscovery finally confirmed the worst fears of wartime families and provided undeniable evidence of what had occurred.