He fought in a morally wrong war at an early age, but struggled for truth and remorse for the rest of his life. The change was guided by his conscience.

He vowed to fight for justice until he died, leaving behind an unfinished mission.

Shiro Azuma, a Japanese veteran, passed away on Tuesday in Kyoto at the age of 93.

After half a century of silent remorse, Azuma published his wartime diary in 1987. He was the first Japanese veteran to openly admit his war crimes.

Azuma was once a young soldier in Japan's Imperial Army. He served for four years with the Japanese forces that invaded China.

He was in China in 1938 and was determined to share his account of the brutality and mass killings he witnessed in Nanjing.

Azuma blamed a system in his country for producing a military that believed human life had no value.

In a few weeks after the invading Japanese troops captured Nanjing in December 1937, they killed more than 300,000 defenceless civilians and unarmed soldiers and raped more than 80,000 women.

Azuma's determination to ask his nation to re-examine its wartime behaviour won him praise and criticism.

Azuma kept fighting in the courts for the right to talk about what Japanese soldiers did to China 68 years ago.

He said his inspiration to share his story came from a Chinese soldier who spared his life at the end of the war, despite having narrowly escaped death under the Japanese occupation.

Azuma's actions may be of little consolation to those who suffered at his hands. But personally, it was a way to make peace with the past.

His diary of Japanese soldiers' terrible wartime atrocities caused him to be ostracized and sued for libel in Japan.

He was constantly molested by rightists. He was sued by a former soldier he described as a war criminal in his diary.

Japanese courts judged three times that Azuma was guilty of fabrication and libel.

Fearing for his life, he retired in a remote village outside Kyoto.

He was a role model for stepping forward and telling his countrymen and the Chinese the truth of what he did, saw and heard about during the war.

Over the years, many Japanese have called on their government to apologize and come to terms with the past.

All of their efforts were obstructed by the ultra-nationalists who claimed the atrocities committed by Japanese soldiers during World War II were made up.

In 1988, Kenji Ono, a scholar and activist, interviewed more than 200 wartime veterans from Aizu Wakamatsu Battalion during the infamous Nanjing Massacre.

His research offered the first Japanese account of the Nanjing Massacre.

Kenji Ono had to live in seclusion for fear of retaliation from the fanatical ultra-nationalists.

Motoshima Hitoshi, mayor of Nagasaki, narrowly survived an assassination attempt by an ultra-nationalist in 1989 for merely saying that Emperor Hirohito was partly responsible for World War II an unpopular view in mainstream Japan. He received death threats and became the city's first mayor to need police protection.

The fact those who dared to present the truth had to hide themselves paints a true picture of Japan's "remorse."

The conduct of the Japanese soldiers on our land should not be wiped from our memory and the memory of our future generations. History tends to repeat itself when one forgets. Azuma tried to keep his conscience alive in his later years.

For clearing his own conscience or sounding an alarm bell for his and younger generations, Azuma deserves reverence.

Facing history squarely is a matter of conscience.