After five minutes of intense firing it was all over. The combined firepower of the defenders, dug in on a ridge, proved too much. When the smoke had cleared the battlefield was littered with corpses.

The skirmish occurred not in one of Indonesia's increasingly rebellious provinces, nor in Mindanao, home to one of the region's longest-running insurgencies, but in stable, safe Singapore. The adrenalin coursing through the soldiers' veins as they fired off their weapons was real enough, but the rest was a hi-tech mock-up. Laser-equipped dummy rifles traced out the bullets' trajectories, as computer-animated "attackers" dodged through the undergrowth on a giant screen.

The venue for the assault was a darkened room on Pulau Tekong, home to the island republic's main centre for turning teenagers into the backbone of the country's armed forces. All Singaporean males must spend at least two years in uniform when they turn 18. "We point the recruits in the right direction, turning them from boys into men for the defence of the nation," says one instructor, surrounded by a platoon of troops with real guns.

The republic's approach to its defence is a rare one in Southeast Asia, where the bulk of men and women under arms are volunteers. Singapore has a professional corps of volunteers too, about 50,000 of them, but the majority of its force is made up of male conscripts. Their involvement does not come to an end after their 24-to-30-month tour, however, as all of them must report for a few weeks' refresher exercises each year. Locally, the country's 300,000 operating national servicemen are described as forming a "people's army", albeit one built around forced service.

Since Singapore's surprise separation from Malaysia in 1965, the political leadership has been acutely aware of the country's vulnerability. Surrounded by much larger neighbours, Singapore is small in terms of population and area. At the time, many commentators did not rate the country's chances of survival. Then prime minister Lee Kuan Yew was determined to prove them wrong, and laid the psychological and literal foundations of today's defence forces. He chose to draft in Israeli military advisers in the early years, labelling them "Mexicans" to conceal their presence from Muslim-majority Indonesia and Malaysia.

To get an idea of just how seriously Singapore takes its defence, one need to look no further than the annual Budget book. Defence spending accounts for almost $3 out of every $10. If home affairs expenditure - outlays for police and prisons - is added in, together with foreign affairs spending, the total rises to 37 per cent. According to the data issued by the Central Intelligence Agency, the cost of Singapore's military represents almost five per cent of gross domestic product. In Indonesia, it is 1.3 per cent, and 1.6 per cent in Malaysia. Analysts say the emphasis is on deterrence, with each service able to call on state-of-the-art weaponry.

The facilities on Pulau Tekong, a small island just off the coast near Changi International Airport, represent a small, but nonetheless vital, part of the defence establishment. It offers three-month courses in basic military training, churning out up to 16,000 fighting men a year. Inductees are rapidly put through their paces, shedding excess pounds on route marches, while learning how to strip down a rifle, thrust a bayonet into an adversary's organs and hurl grenades at defensive positions.

The institution's tone, perhaps contrary to many people's expectations, is far from being brutal or stark. The buildings are pastel-coloured, parents visit three times during basic training and the recruits' mattresses were recently upgraded from thin foam sheets to well-sprung slabs. "We only have three million people in Singapore, of which all males serve in the army. We must take good care of every one," says camp commander Colonel Y. P. Lo. "We want to make sure that we build them up, not break them down."

Not every young Singaporean sees Pulau Tekong, however. Although women may volunteer for the armed services, they do not face compulsory national service. When he was prime minister, Mr Lee wanted to include females when forced inductions started in 1967 but colleagues disagreed. It was one of the very few decisions that went against the influential leader.

The other group that does not make it to the rifle ranges and assault courses, is, in the words of human-rights group Amnesty International, "conscientious objectors". It said that at least 32 were imprisoned last year for their refusal to serve, all of whom were Jehovah's Witnesses. "The men refused to perform military service on religious grounds and were considered to be prisoners of conscience," the group's 2000 Annual Report says.

The government banned the religious group's meetings in 1972 after finding that its members refused to take up arms, salute the national flag or swear oaths of allegiance. According to the United States' State Department: "The [Singapore] government regards such refusal as prejudicial to public welfare and order. While the government has not outlawed the profession or propagation of the beliefs of Jehovah's Witnesses and does not arrest members for merely being believers, the result of [the 1972] deregistration has been to make meetings . . . illegal".

For the willing majority of men, the time spent in the forces has come to be regarded as something close to a national right of passage. Colonel Lo says young men these days are smarter and fitter than they were 20 years ago, quashing suggestions that increasing affluence has spawned legions of effete, cola-swilling teenagers unfit to don combat fatigues. "We find that youth today are more technologically inclined than us," he says.

Back in the darkened room, the defenders stood down from their positions, resting their guns while the computer flashed up assessments of how many "kills" each rifleman could claim. Before long, however, a series of shouted orders prompted magazines to be refitted and barrels to be retrained on the scrub below. The enemy, it seems, may have been beaten off just moments before, but had already regrouped for another desperate charge.