National service has come a long way, from 1967 when Singapore's first national servicemen wore Temasek green combat uniforms, to the present when soldiers don high-tech, pixelised combat uniforms.

More than one million male Singaporeans and second-generation permanent residents have served NS since the maiden batch of 9,000 soldiers were conscripted in 1967.

It has become a rite of passage for young Singaporean men, who form the backbone of the Singapore Armed Forces (SAF).

Currently, Singapore males are conscripted into either the SAF, police or Singapore Civil Defence Force (SCDF), with the majority of the enlistees assigned to the SAF.

Conscription has helped Singapore meet its security needs through the years, but the security landscape is changing rapidly. The Straits Times examines how NS will continue to evolve to meet new challenges.

Q How did NS begin?

A NS became compulsory for all 18-year-old male Singapore citizens and permanent residents on March 14, 1967, when the National Service (Amendment) Act came into effect.

At that time, 10 per cent of the 9,000 called up were selected for full-time service, while the rest served part-time in the People's Defence Force, Special Constabulary and the Vigilante Corps.

Then Defence Minister Goh Keng Swee justified the conscription on the grounds of establishing a credible defence force for the fledgling nation.

In those tumultuous early years, Singapore needed to quickly build up the capability to fend for itself before the British withdrew in 1971.

But it was not easy getting Singaporeans then to come around to the idea. There was resistance, in particular among the Chinese who looked down on soldiering as a profession: There is a Chinese saying that good sons do not become soldiers, just as good iron is not made into nails.

The Chinese community had pushed back when the British colonial government tried to introduce the National Service Ordinance in 1954, which required males between 18 and 20 to register for part-time NS, and be conscripted into the Singapore MilitaryForce or the Civil Defence Corps for training.

The move triggered violent riots.

But Singaporeans came to accept NS just over a decade later, because they had experienced the bloodshed of bombings during Konfrontasi, and the violent racial riots of 1964.

They recognised that security was a burden newly independent Singapore and its citizens had to bear.

NS was gradually expanded to include the police and SCDF.

In 1975, the first intake of full-time police NS officers was enlisted. Six years later, full-time NS was extended to the SCDF.

Q Is NS necessary?

A National servicemen, who form the bulk of the SAF, have allowed the country to respond to challenges such as international piracy, terrorism, and even natural disasters abroad, while at the same time deterring potential aggressors.

Indeed, a strong and credible military force is one of the key cornerstones of the country's foreign policy. Said founding prime minister Lee Kuan Yew in his book Hard Truths: "Without a strong economy, there can be no strong defence. Without a strong defence, there will be no Singapore. It will become a satellite, cowed and intimidated by its neighbours."

In other words, the SAF is essential to preserving Singapore's sovereignty and the way of life that its citizens enjoy.

But NS has also gone beyond just meeting the defence imperative, becoming a cultural institution and part of the Singapore identity over the years. A 2013 study by the Institute of Policy Studies (IPS) showed that more Singaporeans viewed NS as fulfilling a social mission - instilling discipline and values in the young - than as serving a defence mandate.

Dr Goh recognised this function early on in 1967 when he asked Parliament to pass the National Service Bill. He said then: "Nothing creates loyalty and national consciousness more speedily and more thoroughly than participation in defence and membership of the armed forces."

Acceptance of the scheme was also boosted by the fact that no one was exempt from NS. Regardless of wealth or status, every Singaporean male must serve two years of full-time NS, followed by 10 Operationally Ready National Service cycles.

The same 2013 IPS study showed overwhelming support for NS - with 98 per cent of 1,251 respondents saying they supported it.

Q What other countries have conscription?

A Elsewhere, there are a number of places that still draft their citizens into the military.

In Asia, South Korea and Taiwan require young male citizens to serve in the military, for two years and a year respectively.

Both need the military draft to maintain sizeable armed forces for their security needs.

Further afield, countries such as Israel and Norway draft citizens of both sexes into their armed forces.

Sweden, amid brewing tensions in the Baltic region, is reintroducing conscription for both sexes from next year. The country had abolished conscription in 2010, but decided to bring it back after acknowledging that the previous decision was endangering its national security.

In other countries like Finland, young men can choose to serve in the civilian services, in lieu of being conscripted into the military for reasons such as "conscientious objection, inadequate health or political reasons".

Civilian service is usually performed in government bodies or other institutions such as healthcare facilities, retirement homes or pre-schools.

Q How will NS evolve in future?

A NS has changed significantly since its early days, when most enlistees were trained as riflemen in infantry battalions.

The roles of national servicemen have broadened over the years, in tandem with technological advances.

It will likely change even further as the SAF deals with its greatest challenge - falling birth rates.

The Ministry of Defence (Mindef) has said that demographic changes will result in the number of full-time national servicemen (NSFs) shrinking by about 30 per cent by 2030.

Defence Minister Ng Eng Hen called this the SAF's "greatest challenge" in a 2015 speech.

He said: "If you told any CEO that his manpower force will shrink by a third in 50 years' time, he knows that it is a structural change and one that will further increase our dependence on technology."

Experts say the manpower crunch would lead to greater use of robotics and unmanned systems, to make up the shortfall and boost productivity.

Dr Graham Ong-Webb, a research fellow with the military studies programme at the S. Rajaratnam School of International Studies (RSIS), said: "What it means on the receiving end is our boys will go into NS expected to man more sophisticated systems. We have to compensate the lack of manpower with technology-based firepower."

Soldiers are already handling advanced systems now, a trend that is expected to accelerate in future.

The navy is working on a fleet of unmanned vehicles as a countermeasure to naval mines which can be used to detect and dispose of underwater explosives.

The army is also thinking about using "robotic mules" to help soldiers carry heavy loads.

Changes in the security landscape - such as the growing threat of terrorism and cyber attacks - have also led to the creation of new roles for NSFs.

For instance, Mindef is setting up its cyber command - the Defence Cyber Organisation - and recruiting NSFs to groom them into cyber defenders.

It is likely that NS policy will also focus on keeping every serviceman motivated in order to encourage them to contribute meaningfully.

The Government is moving in this direction by allowing NSFs who enlist from November this year to indicate their preferences in vocations.

Meanwhile, falling birth rates have also led to a debate in recent years on whether women should be made to serve alongside their male counterparts. Some feel women could be sent for basic military training where they could be taught medical or infocomm skills.

This could be a "game changer" in helping the SAF plug manpower gaps, said Dr Ong-Webb.

But RSIS defence analyst Ho Shu Huang pointed out that any decision to involve women could have knock-on effects, as such a move would take away a "significant part of the workforce".

A more likely scenario is for volunteers to play a bigger role in helping the SAF in certain niche areas, Mr Ho said.

In 2014, the SAF Volunteer Corps was set up to give women, first-generation PRs and new citizens an opportunity to contribute to national defence. Volunteers can serve in one of 17 vocations, including niche roles such as medical technologists and defence psychologists.

As the security challenges shift, NS and the roles that national servicemen play will move in tandem to meet these challenges.

Said Dr Ong-Webb: "Future warfare is going to be fought in the cyber domain and in the media space.

"We are going to see a significant number of national servicemen being optimised in this way."