A year and a half since China began rapidly building and militarizing artificial islands in the contested, resource-rich waters of the South China Sea, the states most threatened by Chinese expansion are looking for ways to push back more forcefully. But a series of upcoming summits and associated conferences in Southeast Asia will illustrate two key dynamics still playing to China's favor: the widespread reliance on Chinese investment by states in the region and the divides inherent to Southeast Asia that will continue to prevent multilateral regional alliances from unifying against China....