TAIPEI (Taiwan News) — The Ministry of National Defense tracked eight Chinese military aircraft and two official ships around Taiwan between 6 a.m. on Monday (Sept. 16) and the same time Tuesday.

Four of the aircraft crossed the Taiwan Strait median line in the country’s air defense identification zone (ADIZ), according to the defense ministry.

In response, Taiwan sent aircraft and naval ships and deployed coastal-based missile systems to monitor Chinese activity.

So far this month, Taiwan has tracked 251 Chinese military aircraft and 127 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.”