Taiwan's dominance in advanced chipmaking is why the West treats a Chinese takeover as a red line — good for Taiwan's security guarantees, bad for anyone hoping tensions ease.

• Taiwan makes most of the world's advanced chips, which gives it outsized strategic weight.
• If China controlled that supply, it could plant spyware or backdoors in chips used everywhere.
• Europe quietly wants Taiwan to stay independent but does not want to be the one saying it out loud.
• Trump appears content to let the lines harden rather than force the issue.

Outlook: The red line around Taiwan holds until chipmaking can be spread to other countries, which is still years away.