Which weapons could shape a Pacific war?

Which weapon system would have the greatest impact in a future Pacific war?

Likely missiles, especially hypersonic weapons, in open ocean; a South China Sea conflict could produce a different littoral answer.

Geography is the deciding variable rather than one universal weapon. Hypersonic and other missiles dominate the near-term open-ocean answer, but littoral fighting among islands and constrained seas changes engagement ranges and the systems that can matter. In the South China Sea, mines may become especially influential because traffic and maneuver are channelled through confined waters. A Pacific conflict cannot be reduced to one open-ocean weapon comparison.