Taiwan’s defense minister, Chiu Kuo-cheng, said his forces would be compelled to respond militarily if a hostile aircraft or vessel crossed the 12 nautical mile threshold of territorial airspace or sea, including on Taipei-controlled islets off China’s eastern coastline.

“We will give warnings and lock on as it approaches. Locking on also is a form of warning. If it ignores these warnings and continues its approach, then we will act in self-defense,” said Chiu, referring to hostile aircraft or vessels.

The intentions of approaching aircraft would be clarified, he noted. Otherwise, he argued, the assumption is that an intruding aircraft means to do harm.

Chiu made the remarks at the Foreign and National Defense Committee of Taiwan’s legislature, where he told lawmakers a day earlier that he had redefined what Taipei would consider a “first strike” event, widening the scope from a missile or artillery attack to include an airspace incursion by a Chinese military unmanned aerial vehicle.

“If there were a first strike, Taiwan would have to prepare for more,” Chiu told opposition legislator Johnny Chiang.

Asked whether a counterattack by Taiwan’s defenders could start a war, Chiu replied: “Yes. It would be a very serious situation.”

“That is why we emphasize the need to be cautious, and why we were restraining ourselves not to fire rashly a while ago. There’s a reason for that,” Chiu said, appearing to reference Beijing’s August war games, which saw close encounters between Chinese and Taiwanese forces.

Beijing claims Taiwan as its own but has no practical control over the island. Taipei and the Taiwanese public have little interest in a political union with China, which refuses to rule out the use of force to achieve unification.

The Chinese military drills in August—a stated response to House Speaker Nancy Pelosi’s visit to Taipei—brought People’s Liberation Army (PLA) warships and fighter aircraft closer to Taiwan proper than at any time in recent decades. However, they didn’t enter Taiwanese territorial waters or airspace, Taiwan’s defense ministry said at the time.

The drills appeared to be a show of force—Beijing seeking to signal resolve to Taiwan, the United States and others, but China also had no intention of embroiling its military in a major crisis in the lead-up to the Chinese Communist Party’s all-important 20th National Congress, where Xi Jinping is expected to extend his rule as general secretary for another five years.

Yet PLA forces maintain what U.S. officials have called an “elevated posture” around Taiwan, and the risk of an unintentional military incident continues to inform concerns among observers, especially given the lack of mutual trust and crisis communication channels between the cross-strait neighbors.

In the event of a potential incursion, Taiwan would first attempt to intercept any aircraft approaching its air defense identification zone (ADIZ). This buffer acts as a “first line of defense,” said Collin Koh, a research fellow with the S. Rajaratnam School of International Studies at Nanyang Technological University in Singapore.

A hostile aircraft that had either managed to avoid detection in the ADIZ or failed to respond to radio challenges by Taiwan’s air force “would constitute a clear threat” he told Newsweek.

“And of course, the attendant risk is that by setting this red line, the onus is on the other party not to step across it. But [if they did], for reasons that could be a premeditated attempt to provoke or perhaps due to accident, the onus will fall on the party enforcing this red line (in this case Taiwan) to demonstrate that it means business in order to maintain the credibility of this threat of response,” Koh said.

“The end result would be inadvertent or accidental use of force, if either side or both fail to demonstrate restraint,” he said.