This year's Total Defence campaign will focus on strengthening social cohesion and building the country's will to overcome threats that target people's hearts and minds.

Terrorism, fake news campaigns and cyber attacks all "exploit the fault lines in our increasingly diverse multi-ethnic, multi-religious society", the Ministry of Defence (Mindef) said yesterday.

"We will need everyone to step up and play their part to strengthen our unity, resilience and resolve in the face of external pressures," a spokesman said.

Singapore commemorates Total Defence Day today, as Feb 15 marks the day Japanese invaders took over the country in 1942 during World War II.

A series of activities will emphasise the nation's five pillars of defence: economic, social, military, civil and psychological.

In his Total Defence message yesterday, Defence Minister Ng Eng Hen urged Singaporeans to stay vigilant - even during Chinese New Year celebrations.

They can do this through several ways, such as reporting suspicious parcels in public places, alerting the authorities to help someone they suspect is being radicalised or helping to dispel fake news.

The country needs to do so to avoid repeating history, said Dr Ng, noting that the day Singapore fell in 1942 was on Chinese New Year. "Hope was lost as the future seemed ominous and uncertain (then)," he said. "The battle was lost, and so was Singapore."

This year's focus on social and psychological defences echoes a message given by Second Minister for Defence Ong Ye Kung in a speech last month. At a meeting that was part of the annual Shangri-La Dialogue, he emphasised the importance of psychological defence, especially during peacetime.

Citing Finland as an example, Mr Ong, who is Minister for Education (Higher Education and Skills), said it has "a well-established social compact which forms the bedrock of social cohesion and psychological resilience of a people". He noted: "It is a cultural ballast, arguably stronger than military defence."

Fake news is increasingly undermining Singapore's social fabric and unity, he said. "The techniques used are sophisticated, to give the illusion of public interest, legitimacy and support for the falsehoods, and influencing public opinion."

Fighting fake news is also on the agenda of Colonel Joseph Tan Boon Kiat, who runs Nexus, the Mindef department responsible for Total Defence and National Education. He said: "Singaporeans have stood together and weathered crises such as the severe acute respiratory syndrome (in 2003) and haze, with many individuals and groups stepping up to lend a helping hand."

He said psychological defence may not be as apparent, but the nation's "commitment to and personal sacrifices (made) for national service" are "a measure of our inner strength and our people's resolve".

But the new threats warrant a further strengthening in Singapore's social and psychological defences.

"Our increasingly diverse and connected society will make us more vulnerable to those who wish to do us harm," he said.

As part of the Total Defence commemoration, more than 38,000 Secondary 2 students will receive a strategy card game that aims to make them think about Singapore's five pillars of defence.

Greendale Secondary student Chinta Kunta Shreya, 13, who learnt how to play it last year, said: "When I drew a cyber-attack card, my social defences were weak and I lost the game. I have learnt my lesson."