The balance of power in Southeast Asia has been quietly shifting in China's favor, and perhaps no country feels it more than Vietnam. In the span of a few months, Hanoi -- once the staunchest advocate for the Trans-Pacific Partnership (TPP) -- became the first participant to shelve the trade pact, well before U.S. President-elect Donald Trump announced his intention to withdraw from it. At the same time, Vietnam softened its criticisms of China and took steps to mend ties with Beijing. Rather than positioning itself squarely in China's crosshairs, Hanoi began a more subtle pursuit of its maritime claims and alliances with stronger partners, keeping its options open and its defenses ready.
More so than most of its neighbors, Vietnam can neither fully reject nor embrace the growing power on its northern border. Some, such as the Philippines and Malaysia, have eagerly joined Chinese-led trade blocs and dispute-settling mechanisms. Others,...
