Under the code of his secret wartime army unit, which experimented with chemical weapons on live prisoners and dropped bombs to spread plague bacteria through northern China, Yoshio Shinozuka should not be alive today.
As a member of the Japanese biological warfare outfit, known as Unit 731, Mr. Shinozuka was told that if he ever faced capture by the Chinese, his duty to Emperor Hirohito was to kill himself rather than compromise the secrecy of a program that so clearly violated international law.
Mr. Shinozuka was captured and imprisoned for years in China, but he survived. Now, 55 years later, he is a hale 77-year-old. But still haunted by remorse, he has spoken, too -- providing the first account before a Japanese court by a veteran about the workings of the notorious unit.
No previous suit seeking damages for atrocities committed by the Imperial Army has made it this far in a Japanese court, lawyers and historians here say.
That this case, now in its final stages, has not been dismissed like so many others is due in part to painstaking legal research and to cooperation over strategy by some of Japan's leading lawyers.
Lawyers who have sued the government say the fact that this case has become the first in which a judge has allowed the extensive introduction of evidence instead of handing down a quick dismissal may also attest to an important shift under way on the issue of reparations.
Japanese officialdom has long rejected the concept out of hand as inapplicable under the terms of the 1951 San Francisco Treaty, which officially ended the war.
Testifying late last month in a lawsuit brought by more than 100 of his unit's surviving Chinese victims, Mr. Shinozuka told in excruciating detail how he had witnessed men being injected with the plague and then dissected while still alive.
As a member of the Japanese Army youth corps, it was his duty to wash the victims with a hose and a deck brush before the operations began. ''When I finished, the surgeon applied a stethoscope to his chest and listened to his heartbeat,'' he said, describing his first experience of such an experiment. ''As soon as he lifted the stethoscope, the dissection began.''
Mr. Shinozuka was the first of several veterans of the unit who in the last month have described their actions. They also testified that some prisoners had been deliberately frozen to death and some had been injected with lethal chemicals and germs to study the efficacy of those agents as weapons.
The veterans' role is vital to this legal action, already regarded here as one of the most important to bring Japan to account for the worst episodes of its wartime past.
But as significant as this lawsuit is, part of its power resides in the fact that it is one of many. In its own courts and in lawsuits abroad, Japan is increasingly under siege -- in many cases by aged victims pressing claims for damages. And the pressure may finally be creating a sense of urgency here for settlement.
Last week in Tokyo, private Japanese and international organizations convened a war tribunal that found Japan's military leaders, including Emperor Hirohito, guilty of crimes against humanity for the sexual slavery imposed on tens of thousands of women in countries controlled by Japan during World War II.
The tribunal has no legal power to exact reparations for the survivors among these so-called comfort women. But with its judges and lawyers drawn from official international tribunals for the countries that once were part of Yugoslavia and for Rwanda, it brought unparalleled moral authority to an issue scarcely discussed or taught about in Japan.
Last month, a major Japanese construction company, the Kajima Corporation, acknowledged before a Japanese court that Chinese laborers were worked and tortured to death in slave-like conditions in Japanese factories during the war. In an out-of-court settlement encouraged by the judge, the company offered $4.6 million to the victims' relatives.
And Mitsubishi Heavy Industries, which has been fighting reparations claims for years, agreed to meet this week with about 50 plaintiffs in two lawsuits who say that they or relatives who died suffered in the slave labor conditions enforced by the company on captive foreign workers.
Japanese legal experts and historians say the floodgate has opened as a result of a complex set of circumstances. For one, the compensation settlements for victims of the Nazis reached in recent years with German and Swiss companies have increased pressure on the Japanese government and Japanese companies to do the same.
But foremost, these experts say, has been the democratization of South Korea and increased freedoms in China that have accompanied the end of the cold war. This more open atmosphere has for the first time allowed large numbers of individuals to pursue claims for damages against Japan. ''During the cold war situation, Japan just didn't have to face the issues of the past,'' said Hiroshi Tanaka, a professor of history at Ryukoku University. ''We could always get by just ignoring it. Japan was under the umbrella of the United States, and America settled Japan's Asian issues.''
From the official Japanese perspective, where war crimes are concerned there is nothing more to be settled. The government has insisted, and Japanese courts have largely agreed, that Japan's responsibility was ended with the reparations paid under the San Francisco Treaty.
But in one measurement of how decisively the ground has shifted under Japan's no-compensation stance, even many relative hard-liners on the issue like Hiroaki Kobayashi, a law professor at the University of Japan who vehemently opposes paying official reparations, say that Japanese people must find other ways to aid their victims and face their country's guilt.
''In the 1990's Volkswagen paid individual compensation in the amount of 10,000 marks per person,'' Professor Kobayashi said, ''and that could be some kind of yardstick for us. We should establish some kind of fund, call it an international friendship fund. The Japanese government could cover half the amount, and the companies that used forced labor could support the other half of the cost. A lot of people are still suffering from this war, and every Japanese has a responsibility to help pay for this.''
Meanwhile, as sentiment builds quietly in favor of limited payments, official Japan's unyielding position is facing ever-stiffer attack. ''Legal theories to counter the government's arguments are making big advances,'' said Kohken Tsuchiya, the lead lawyer in the case and a former president of the Japan Bar Association. ''There have been 40 to 50 compensation cases brought in the past, and the lawyers involved have formed a network, sharing notes and ideas to break down the government's arguments. The goal is to interpret the Hague treaty in such a way as to allow individuals to make claims against governments.'' The treaty set out rules of war, including the rights of those taken prisoner.
Others, meanwhile, are focusing on the ''comfort woman'' issue, saying that since war crimes against women were not even taken into consideration by the international tribunal that tried Japan's leaders after the war, they should not be covered by the San Francisco Treaty.
Yuan Zhulin, 78, a Chinese woman who was one of several former sex slaves to testify, explained that she had been kidnapped at age 16 after being told she would be given a job washing dishes at a hotel.
''Every day there was a line of soldiers, with ticket in hand, waiting to have sex with me,'' she said. ''All of the soldiers were simply inhumane. I used to hurt so badly that I couldn't sit down, or even sleep.''
Gabrielle Kirk McDonald, a former leader of the international Criminal Tribunal for the Former Yugoslavia, said the San Francisco Treaty ''was designed to resolve property issues.'' She said Japan's leaders, including Emperor Hirohito, knew of the ''comfort stations'' for Japanese soldiers, which involved the effective sexual slavery of 200,000 or more women, by some estimates.
''The notion of command responsibility was established at the Nuremberg Trials and holds commanders responsible either when they knew of, or should have known of, atrocities being committed,'' she said.
Asked why he had wanted to cooperate with the continuing trial involving Unit 731, Mr. Shinozuka delivered a long and highly personal meditation on guilt and forgiveness. ''The government made no apology at the time,'' he said, ''and has kept the same attitude ever since. They remain silent.
''But all these years I've thought about who received the germs I created, and how much they must have suffered. I thought about the bereaved, and about the survivors, people whose lives were forever damaged. I thought about the victims of vivisection, and I felt these acts must not be buried away, or else we are condemned to go from darkness to darkness.''
Photo: Yoshio Shinozuka, left, a veteran of the Japanese biological warfare outfit in World War II, commuting to his home from Tokyo, where he has been testifying about lethal experiments conducted on Chinese prisoners. (Stuart Isett for The New York Times)