Ken Burns was in his studio working on the final edits of a forthcoming documentary film series on the American Revolution when he learned on Tuesday that the historian William E. Leuchtenburg had died at 102.

“I had to get up and go be by myself for a while,” Mr. Burns said in an interview. “Everything just crashed to a halt.”

In his view, Mr. Leuchtenburg was “one of the great historians, if not the dean of American historians in the United States, for his work on the presidency.”

For more than 40 years, Mr. Leuchtenburg was a close adviser and friend to Mr. Burns, appearing in three of his documentaries — “Prohibition” (2011), “The Roosevelts: An Intimate History” (2014) and “Benjamin Franklin” (2022) — and consulting on many more.

The Times spoke to Mr. Burns on Wednesday about Mr. Leuchtenburg’s career. His observations, lightly edited and condensed for clarity, are below.