When a veteran American diplomat met a Syrian rebel commander in 2023, they had a surprisingly cordial chat about their lives on enemy sides in two Mideast wars.

The commander, who went by the name Abu Mohammed al-Jolani, recalled when he was a young jihadist shooting at the mobile homes in Baghdad where the diplomat was living after the American invasion of Iraq in 2003.

The diplomat, Robert S. Ford, recounted that in 2012, as ambassador to Syria during its civil war, he had shut the U.S. Embassy for fear that the commander’s Al Qaeda faction would bomb it.

The Syrian rebel leader then talked about what he envisioned as his next act, seizing the capital and governing Syria — a prospect that appeared fantastical at the time, Mr. Ford told The New York Times.

Last December, the commander did just that.

He led a startling offensive that toppled the dictator Bashar al-Assad, and became president of Syria. He swapped his military garb for sharp suits and exchanged his nom de guerre for his real name, Ahmed al-Shara.