Taiwan will extend compulsory military service from four months to one year, President Tsai Ing-wen announced on Tuesday, stressing that the island must prepare for growing threats from China.
"The current four-month military service is not enough to respond to the constantly and rapidly changing situation," she told a news conference.
"We have decided to restore one-year military service from 2024," she added.
The reform will apply to all men born after January 1, 2005, she said.
The democratic island of Taiwan of 24 million inhabitants lives under the constant threat of an invasion from China, which considers it part of its territory to be reconquered one day, and if necessary by force.
The announcement comes two days after Chinese military exercises near Taiwan that Beijing says it organized in response to "provocations" and "collusion" between Washington and Taipei.
"Nobody wants war... but, my compatriots, peace will not fall from the sky", declared the president again.
Under President Xi Jinping, Beijing has stepped up military, diplomatic and economic pressure on Taiwan as relations deteriorated.
The prospect of a Chinese invasion is increasingly worrying Westerners and many of China's neighbors.
Re-elected in October for a third term as China's leader, Xi made it clear that the "reunification" of Taiwan could not wait for future generations.
In the event of a conflict, the island of Taiwan is largely exceeded in terms of manpower, with 88,000 soldiers in the army, against one million for Beijing, according to Pentagon estimates. Beijing also has a considerable advantage when it comes to military equipment.
Taiwan has stepped up training for reservists and increased purchases of fighter jets and anti-ship missiles to bolster its defenses. But experts say that's not enough.
Once unpopular, compulsory military service was introduced by a military dictatorship before the mountainous island became a progressive democracy.
The previous government in Taipei had shortened it from one year to four months, preferring to develop an army of recruits.
But recent polls show that more than three-quarters of Taiwanese find this duration too short.
The military is also struggling to recruit and retain full-time personnel due to weak financial incentives.
Ms Tsai described her decision to extend military service as 'extremely difficult' but described it as 'designed to secure the democratic way of life for our future generations'.
China and Taiwan have been separated since the end of the Chinese Civil War in 1949, and the Taiwanese president has said joining China is not acceptable to Taiwanese.