The submarine did not know she was carrying prisoners – all men - who had been captured when Rabaul was invaded by the Japanese Imperial Army in February 1942.

She sank with at least 850 Australian service members and 210 civilians from 14 countries, ranging from a boy aged 15 to men in their sixties.

Montevideo Maru was found at a depth of more than 4,000 metres during a mission by Sydney’s Silentworld Foundation, a group dedicated to maritime archaeology and history, and the Dutch company, Fugro, deep-sea survey specialists, which supplied the search vessel, the Fugro Equator.

With support from Australia’s Department of Defence, the search began on 6 April 110 km north-west of Luzon in the Philippines.

Fugro Equator team members pose for the camera after another successful expedition (Max Uechtritz)

The expedition team included members of the Rabaul and Montevideo Maru Society, established in 2009 to memorialise the Montevideo Maru, pay tribute to the victims and their families and, if possible, locate the ship.

On 18 April, after just 12 days, a positive sighting was recorded using technology including an autonomous underwater vehicle.

It had taken nearly five years of research and planning by Silentworld before it was ready to assemble the expedition team, led by Silentworld director, Australian businessman, philanthropist and explorer John Mullen.

“The discovery of the Montevideo Maru closes a terrible chapter in Australian military and maritime history,” Mr Mullen said.

“Families waited years for news of their missing loved ones, before learning of the tragic outcome of the sinking. Some never fully came to accept that their loved ones were among the victims.

“By finding the vessel, we hope to bring closure to the many families devastated by this terrible disaster,” Mullen said.

“I would like to express my gratitude to all of the dedicated Silentworld team involved in this expedition, to the outstanding Fugro crew and technical team on board the Fugro Equator, and to the Australian Department of Defence for their unwavering support.

“I am proud to be the citizen of a country that never forgets or stops looking for those lost in the course of duty, no matter how many years may pass,” he said.

No family suffered more from the tragedy than the Turners of NSW. Their three inseparable young sons, Sidney, Dudley and Daryl, enlisted together in Australia’s first commando group, the 1st Independent Company – and perished together when Montevideo Maru sank.

Australian Andrea Williams, a founding member of the Rabaul and Montevideo Maru Society, was on board Fugro Equator when the wreck was discovered. Her grandfather and great uncle died in the tragedy

“This is an extraordinarily momentous day for all Australians connected with this tragic disaster,” Ms Williams said.

“Being part of the Silentworld team that found the wreck has been hugely emotional and fulfilling.

“Having had a grandfather and great-uncle as civilian internees on Montevideo Maru meant the story was important to me, as it is to so many generations of families whose men perished.

“I could never understand why it was not a more powerful part of Australia’s World War II history.’

The wreckage of the Montevideo Maru, sitting at a deeper depth than the Titanic, will not be disturbed. No artefacts or human remains will be removed.

The site will be recorded for research purposes out of respect for the families of those on board who were lost.

Chief of the Australian Army, Lieutenant General Simon Stuart, said finding the wreck has ended 81 years of uncertainty for the loved ones of the lost.

“The Australian soldiers, sailors and aviators who had fought to defend Rabaul met a terrible fate at sea on the Montevideo Maru,” he said.

“We remember their service and the loss of all those aboard, including the 20 Japanese guards and crew, the Norwegian sailors and the hundreds of civilians from many nations.

“I want to thank the Silentworld team and the dedicated researchers, including the Unrecovered War Casualties team of the Army, who had never given up hope of finding the final resting place of the Montevideo Maru.

“A loss like this reaches down through the decades and reminds us all of the human cost of conflict. Lest We Forget,” Lieutenant General Stuart said.

Descendants of the Montevideo Maru can link here to register and be kept informed. Details of commemorative events will be provided later.