What happened
The election capped what Lee himself called a "quiet revolution": Taiwan moved from a one-party authoritarian state under martial law (lifted in 1987, ending 38 years of emergency rule that had included the mass political imprisonment and executions of the White Terror) to a fully competitive multi-party democracy within less than a decade, without a civil war, a coup, or a violent revolution — a genuinely unusual transition by the standards of most democratisation processes elsewhere in the world.
China's response to the prospect of a free vote it could not control was the so-called Third Taiwan Strait Crisis: missile tests landing in waters near Taiwan's major ports and large live-fire military exercises timed deliberately around the election, intended to pressure voters against candidates China viewed as pro-independence. Taiwanese voters did not respond as Beijing likely hoped — turnout was high and Lee won comfortably. The crisis set the template for a pattern that recurs throughout this file: Chinese military pressure calibrated to Taiwanese domestic political events, a dynamic documented in Beijing's own state media and military statements rather than only in Taiwanese or Western sources.