Median.

This is coolbert:

Don't think so much the Taiwanese ADIZ. Air Defense Identification Zone. 

Think rather the Median Line. Referred to by some as the Davis Line.

ROC = Republic of China. Taiwan.

Chinese naval forces crossing the Median Line moving from west to east the Taiwan Strait considered a provocation to be taken seriously.

This image [click on image to see an enlarged view] shows the Taiwanese ADIZ and the dashed Median Line [Davis Line]. Warplanes in the ADIZ required to ID themselves. Taiwanese numbers of ADIZ violations inflated as a result? The dashed Median Line not running directly through the center of the Taiwan Strait. Chinese warships sailing eastward of the line considered a threat to Taiwan for which a obligatory response required.

"Taiwan Strait median line coordinates revealed"

"Taiwan defense ministry denies reports of Chinese military drills held across line"

Story from www.taiwannews.com.tw by Huang Tzu-ti 2019/07/30.

"TAIPEI (Taiwan News) – Taiwan’s defense ministry on Tuesday (July 30) refuted reports that the military drill carried out by China on Monday took place across the median line of the Taiwan Strait."

"In a press conference, the Ministry of National Defense (MND) provided the officially recognized coordinates of the median line: 27°N, 122°E (north) and 23°N, 118°E (south). The announcement marked the first time in 15 years that the government of Taiwan has clearly defined the line separating the two sides across the strait, reported the Central News Agency."

[....]

"The last time Taiwan published the coordinates of the median line was in May of 2004. That information was consistent with the coordinates announced today."

My best approximate rendering of the median line. Chinese warships crossing the median line moving from west to east seen by the Taiwanese as a provocation and a matter to call for higher alert of the ROC armed forces. [Click on image to see an enlarged view]

That Taiwan ADIZ and even the Median Line [Davis Line] creations of American general officers. The ROC and Red China confrontation post-WW2  seen by many USA experts as a possible for nuclear confrontation. Obvious the USA military would have great say in such matters. But that has been over sixty years now.

coolbert.