When the first National Memorial Day for Victims of the Nanjing Massacre was held on Dec 13, 2014, some people questioned the need to remember the incident in 1937.

The answer comes easy to anyone who has ever paid a visit to Nanjing: The Japanese army committed horrendous crimes in the then capital of the country, so there is no choice other than to remember what transpired to avoid similar crimes being committed again. The invaders killed disarmed military personnel and civilians alike, raped women and burned large parts of the once prosperous city to ashes. Their rampage claimed more than 300,000 lives in a few weeks.

All historical evidence also shows that the Imperial Japanese Army committed the atrocities intentionally and it was all planned, not the "spontaneous deed of individual soldiers". Even Nazi Germany's embassy in Nanjing recorded the brutality committed by their allies; some Germans in Nanjing then tried to save lives.

Nanjing definitely epitomizes some of the cruelest acts humans can inflict on others. However, it is not as widely known in the West as, say, the Holocaust.

Right-wing politicians in Japan take advantage of this. They seek a return to Japan's militarist past despite it having brought untold sufferings to people in the Asia-Pacific.

To prevent the ghost of Japan's militarist past from returning to life, it's necessary to create awareness in the field of international public opinion and nail this shameful part of the country's past to the pillar of shame forever.

The Nanjing Massacre must be remembered so that similar atrocity does not occur again. On Wednesday morning sirens shrilled across Nanjing, and everybody who heard them observed a moment of silence. It's time the Japanese politicians observed the same with their conscience.