The United States would achieve three objectives by purchasing a number of Shortfin Barracuda submarines from France and then giving them to Vietnam. First, the Biden administration would repair relations with America's oldest ally. Second, it would supply a rising security partner with newly potent means of challenging China's imperialism. Third, it would test President Emmanuel Macron's commitment to international security in the South China Sea. This option bears note as France rages over Australia's cancellation of a submarine contract worth tens of billions of dollars. France is mixing justifiable anger (it has lost a lucrative contract worth thousands of...