True, 武力強占 is the only way,

but China doesn't have to shout 武力強占 at every moment. And China cannot 武力強占 all the islands at the same time.

I think right now China is talking about 共同開發 all the time, but doing 武力強占 one island a time.

30-40 years ago, China airforce and navy were weak. China could control only 西沙，then take cared 中沙，now is working on 南沙.