To understand the loss of the civilian men on the Montevideo Maru you have to understand the politics which led to the Japanese decision to transport them with the enlisted men to Hainan.
Possibly as early as 1943 the Australian Government had information that the men from Rabaul had been loaded onto a ship destined for Hainan and that it had been sunk. Evidence suggests that it was definitely known by 1944. The dropping of letters in 1942 wasn’t, as Hank Nelson states, “a strange act of chivalry in a brutal war” it was one of a series of calculated acts by the Japanese aimed squarely at showing the Australian Government that they were prepared to give fair treatment to prisoners of war.
The problem for the Japanese top echelon who devised this campaign of fair treatment and letter dropping was the Tol massacre. It's possible that the Japanese H.Q. in Rabaul knew nothing of this massacre till after the war.
With the return of the survivors of the Tol massacre to Australia in early 1942 the government knew that men it had abandoned as hostages to fortune had been massacred. It immediately assembled a court to inquire into the whole of the circumstances attending to operations in Rabaul. The court completed its investigation in May 1942, one month before the sailing of the Montevideo Maru. Frank Forde deputy Prime Minister and Minister for the Army sent a cable to Curtin reassuring him that the inquiry had found that nurses at Vunapope were being well cared for.
Although the courts findings weren't made public the Chifley government used it as an excuse not to conduct a further inquiry into the loss of the Rabaul men post war. The refusal to investigate the events in Rabaul, and the loss of the men on the Montevideo Maru, has led to much speculation and various theories being put forward to explain what happened. Most of the theories have loose ends that can't be tied together. I suggest that these loose ends have clouded the issue for many years. Even the Rabaul survivors of that time, the nurses and officers who made it to Japan, the writings of Gordon Thomas and missionaries can only describe what happened, not why it happened.
Finding the wreck of the Montevideo Maru would not be easy as it lies at a great depth. Having said that, it would be much easier and possibly a lot cheaper to find than the wreck of the Sydney, as the coordinates of where it was torpedoed are known. It would be a simple matter for the government to recognise the enormous tragedy of the sinking of the Montevideo Maru and give the families of those who lost loved ones some closure.
I personally believe that there is far more to the story of the movement of the civilian internees from Rabaul to Hainan than has yet been discovered in our archival files. Possibly therein is where the problem lies.
It was, and possibly still is, all about politics.
Source: Forum - Website of the Papua New Guinea Association of Australia. A 'Montevideo Maru' task force will meet on Tuesday to begin a major effort to persuade the Australian Government to locate the ill-fated vessel and to resolve other aspects of the tragedy.