[duff]

First, let me suggest pick a timeline of events which suit what you want to design and go with it.

Politically there is tension between China and: Philippines, Japan, Vietnam, over ownership of islands which would support a claim to exploit valuable ocean. Without suggesting there is likely to be military conflict it would not (in my opinion) be too big a stretch to build a camp/scenario based around very limited military clashes over the islands (maybe commando raids on islands or naval bases). A more thoroughly hypothetical choice could see the clashes get bigger.