Trump, the Insurgent, Breaks With 70 Years of American Foreign Policy

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Nearly a year into his presidency, Mr. Trump remains an erratic, idiosyncratic leader on the global stage, an insurgent who attacks allies the United States has nurtured since World War II and who can seem more at home with America’s adversaries. His Twitter posts, delivered without warning or consultation, often make a mockery of his administration’s policies and subvert the messages his emissaries are trying to deliver abroad.

Mr. Trump has pulled out of trade and climate change agreements and denounced the 2015 nuclear deal with Iran. He has broken with decades of American policy in the Middle East by recognizing Jerusalem as the capital of Israel. And he has taunted Kim Jong-un of North Korea as “short and fat,” fanning fears of war on the peninsula.

He has assiduously cultivated President Xi Jinping of China and avoided criticizing President Vladimir V. Putin of Russia — leaders of the two countries that his own national security strategy calls the greatest geopolitical threats to America.

Above all, Mr. Trump has transformed the world’s view of the United States from a reliable anchor of the liberal, rules-based international order into something more inward-looking and unpredictable. That is a seminal change from the role the country has played for 70 years, under presidents from both parties, and it has lasting implications for how other countries chart their futures.