WASHINGTON — This week’s gathering of the annual United Nations General Assembly was dominated by President Trump.

He emphasized his “America First” vision in his speech to the assembly and at a rambling news conference the next day. In smaller meetings, he touched on global issues that continue to vex the United States and other nations — from North Korea’s nuclear program to election interference by foreign powers. And he shrugged off laughter from other world leaders at his typically boastful words.

“I was struck by how he wanted to use this audience and this opportunity to reject some of the key tenets of global multilateralism,” said Dafna Rand, a former State Department official who is now vice president for policy and research at Mercy Corps, a humanitarian aid organization.

“He was using this speech to reject the very premise of the U.N.,” she said.

Between espousing those ideas, Mr. Trump and his senior administration officials detailed specific policy positions and gave a clearer view into how the United State is grappling with some big dilemmas. Here are five takeaways on their vision of United States foreign policy, as presented at the world body’s summit meeting.