U.S. President Joe Biden attends a welcoming ceremony hosted by Vietnam’s Communist Party General Secretary Nguyen Phu Trong at the Presidential Palace of Vietnam in Hanoi on Sept. 10, 2023. SAUL LOEB/AFP via Getty Images hide caption toggle caption SAUL LOEB/AFP via Getty Images U.S. President Joe Biden attends a welcoming ceremony hosted by Vietnam’s Communist Party General Secretary Nguyen Phu Trong at the Presidential Palace of Vietnam in Hanoi on Sept. 10, 2023. SAUL LOEB/AFP via Getty Images Last summer, as the United States and Vietnam finalized plans to upgrade the bilateral relationship, the Communist leadership in Hanoi issued a secret directive that aimed to limit outside influences and protect the party’s grip on power in the face of growing exposure to the U.S. and its allies. Analysts say the six-page document — known as “Directive 24” and issued by the ruling Communist Party’s elite Politburo — offers a window into the motivations and concerns of party leaders as they committed to deepen Vietnam’s links with an erstwhile enemy and leverage shifting geopolitical sands …