Last month, the USS Carl Vinson became the first American aircraft carrier to visit Vietnam since the Vietnam War ended in 1975. Coming alongside the news that a record 23 nations from Southeast Asia and beyond would be joining biennial naval exercises in the eastern Indian Ocean, it was a potent reminder of just how eager the nations surrounding the South China Sea are to embrace powerful allies to fend off a rising China.

But as Beijing's regional clout continues to grow, it can be hard for weaker nations to resist it, even with these allies' support. Barely three weeks after the Carl Vinson's visit, the Vietnamese government bowed to Chinese pressure and canceled a major oil drilling project in disputed South China waters.

It was yet another sign of the region's rapidly shifting dynamics. For the last decade, the United States and its Asian allies have been significantly bolstering their military activities in the region with the explicit aim of pushing back against China. But Beijing's strength and dominance, along with its diplomatic, economic and military reach, continue to grow dramatically.