The new recruits arriving in Taiwan's western city of Taichung on Thursday are the first batch taking part in the island's one-year mandatory military service -- an extension from the previously obligatory period of four months.

The extension was first announced in 2022, and is part of President Tsai Ing-wen's plan to bolster the self-ruled island's defences in the face of an increasingly aggressive China.

Despite Taiwan having its own government, currency and military, Beijing claims the island as part of its territory and has in recent years upped the rhetoric of "unification" being "inevitable".

China has never renounced the use of force to try and bring Taiwan under its control and has maintained a near-daily military presence around the island.

Welcoming the new recruits on Thursday, Hong Hsin-chi, commander of the training camp, vowed to be "strict but not harsh".

He said the armed forces have added "more professional courses" to boot camp such as combat, quick-fire training and combat first aid.

After eight weeks of training, they will be transferred to different branches of the military.

"When they graduate, they will be qualified soldiers," Hong said.

The first batch of 670 recruits -- who are all men aged 18 or 19 -- will be reporting to three training centres across Taiwan.

- 'My duty' -

The conscription age in Taiwan is 18, with deferment granted for higher education -- though all men are required to serve in the military by the time they turn 36.

Mandatory service used to be deeply unpopular in Taiwan, and its previous government had reduced it from one year to four months with the aim of creating a mainly volunteer force.

But polls in recent years have shown increasing support for a longer period of service -- a sentiment that has grown as China has become more vocal about its claims over Taiwan.

When Tsai reinstated the one-year period in December 2022, she said it would apply only to men born after January 1, 2005, calling it "an extremely difficult decision... to ensure the democratic way of life for our future generations".

The announcement was made months after Beijing ran its largest-ever war games around Taiwan -- coming as then-US House speaker Nancy Pelosi visited the island.

Since then, China has deployed warplanes and naval vessels around Taiwan on a near-daily basis as a "grey zone" tactic that experts say stops short of an outright act of war.

At Taichung's army camp on Thursday, the young men were first taken to a row of soldiers in white coats who took notes as they did a preliminary physical test -- squatting, extending and raising their arms.

They were seated in orderly rows and stared steely ahead as women wearing camo-patterned hats swiftly shaved their heads.

"I willingly accept our country's change in policy to extend (conscription) to one year," said uniformed recruit Yin Hsin-shi. "As a citizen of the Republic of China, Taiwan, this is my duty."

While he admitted to being "a bit nervous" when he received his draft notice, Yin said he felt reassured once he arrived at the camp.

"My superiors and instructors are not as terrifying as they say."