Tom Brenner/The New York Times/Redux

Months of planning and negotiating took place before the first summit. A low point occurred a year before when North Korea sent home Otto Warmbier, an American college student it had jailed. He never regained consciousness after arriving back in the US, and later died. Trump and Kim traded insults about missile tests. But Trump remained open to a meeting. A high point came when North Korea freed three American prisoners , who Trump met in person when they arrived at Andrews Air Force Base just a month before his first summit with Kim. The prisoners included Tony Kim, left, Kim Hak-song and Kim Dong Chul. Also pictured is Secretary of State Mike Pompeo. Later that month, Trump briefly canceled the summit in a letter to Kim before putting it back on schedule.