This week’s long-awaited summit between U.S. President Donald Trump and Chinese President Xi Jinping may be among the most consequential encounters between leaders of the two countries since President Richard Nixon met Chairman Mao Zedong in 1972. I played a role in planning that earlier summit as senior economic adviser on the National Security Council under Henry Kissinger; its historic success depended on both the meticulous preparation of the two leaders and their top officials and the clarity and precision with which they stated their positions and resolved their differences. Although that history may not have shaped the Trump administration’s preparations in recent weeks, Chinese officials have no doubt studied those lessons in their own preparations—and incorporated them into their plans for Xi’s discussions.…