In PRC's case, it's also just a generic nuclear build up because the hereto alleged ~300 nukes was minimal (really poverty) deterrance posture that became no lo

In PRC's case, it's also just a generic nuclear build up because the hereto alleged ~300 nukes was minimal (really poverty) deterrance posture that became no longer tenable now that war with US is possible. Other parts of triad is being worked on as well. Apart from geopolitics, what drove PRC nuke buildup was US modernizing warheads for better detonation timing so less missiles needed for hardened targets = same controlled stockpile can strike 2-3x more targets. It wasn't better missile defense, but better missile offense. I'd argue better missile defense drive adversaries to develop better missiles tech which are dual use and will enhance their conventional capabilities and perhaps create more vunerabilities overall.