Singaporean Prime Minister Lawrence Wong posted on social media on Sunday that the day marked Singapore's Total Defence Day, which also commemorates the fall of Singapore to Japanese forces in 1942, beginning a dark chapter in the nation's history.

"The suffering of those years left us with a hard but enduring lesson: we must always be masters of our own destiny. No one else will defend Singapore for us," Wong said in his post.

"In today's divided and dangerous world, this lesson carries greater weight," said Wong. "We may be a small nation. But our strength has never been in numbers alone. It is in our collective will and resolve to protect our home and our way of life."

Singapore held a memorial ceremony on Sunday to honor civilians who died during the Japanese occupation in World War ll. About 500 people attended the annual observance in the city center. The event was organized by the Singapore Chinese Chamber of Commerce and Industry and the Central National Education Office of the Ministry of Defense, the Xinhua News Agency reported.

"It was a time of tremendous hardship and suffering," said Singapore's Education Minister Desmond Lee in a speech, noting that tens of thousands of people were rounded up and killed, thousands were forcibly conscripted to build military installations, and many families lost loved ones to starvation or execution.

"We cannot, we must not, and we will not forget this painful history," Lee said.

On February 15, 1942, Singapore fell to the invading Japanese army, marking the start of more than three years of occupation. Historians estimate that at least 50,000 Chinese Singaporeans were killed by Japanese forces during the occupation, according to Xinhua.

On February 15, 1967, Singapore established the Civilian War Memorial and designated the date as Total Defence Day. Since then, annual remembrance ceremonies have been held at the memorial every February 15.