The People’s Republic of China has been conducting a sustained campaign of pressure against Taiwan that falls below the threshold of armed attack and above the threshold of normal competitive statecraft. This gray zone — the space between peace and war where coercion operates through ambiguity, exhaustion, and the deliberate exploitation of thresholds — has been the primary arena of Chinese pressure on Taiwan for years and is the operating environment that Taiwan’s defense establishment spends more of its daily attention managing than any invasion scenario.

For most of the past five decades, an informal boundary ran down the center of the Taiwan Strait. Neither side formally acknowledged its existence. Neither side inscribed it in any treaty or agreement. Both sides, for most of the period between the 1950s and 2020, generally respected it: Taiwanese and Chinese military aircraft and naval vessels operated on their respective sides, and crossings were infrequent enough to be noteworthy events that required diplomatic management. The median line was a fiction that worked because both sides found it useful. China has now decided it no longer finds it useful, and the consequences of its erasure are visible in daily military operations across the strait.