TAIPEI (Taiwan News) — The Ministry of National Defense detected 21 Chinese military aircraft and one official ship around Taiwan between 6 a.m. on Friday (Sept. 13) and the same time Saturday.

Seventeen of the People’s Liberation Army (PLA) aircraft crossed the Taiwan Strait median line in the country’s northern and southwestern defense identification zones (ADIZ), according to the defense ministry.

In response, Taiwan sent aircraft and naval vessels and deployed coastal-based missile systems to monitor the situation.

So far this month, Taiwan has tracked 230 Chinese military aircraft and 105 ships. Since September 2020, China has increased its use of gray zone tactics by incrementally increasing the number of military aircraft and naval vessels operating around Taiwan.

Gray zone tactics are defined as “an effort or series of efforts beyond steady-state deterrence and assurance that attempts to achieve one’s security objectives without resort to direct and sizable use of force.”