A new understanding of the post World War II era, showing what occurred when the British Empire wouldn't step aside for the rising American superpower-with global insights for today.An enduring myth of the twentieth century is that the United States rapidly became a superpower in the years after World War II, when the British Empire-the greatest in history-was too wounded to maintain a global presence. In fact, Derek Leebaert argues in Grand Improvisation, the idea that a traditionally insular United States suddenly transformed itself into the leader of the free world is illusory, as is the notion that the British colossus was compelled to retreat. The United States and the U.K. had a dozen abrasive years until Washington issued a "declaration of independence" from British influence. Only then did America explicitly assume leadership of the world order just taking shape.Understanding all of this properly is vital to understanding the rise and fall of superpowers, why we're now skeptical of commitments overseas, how the Middle East plunged into disorder, why Europe is fracturing, what China intends-and the ongoing perils to the U.S. world role.