“One of McChrystal’s hardest lessons was his government-in-a-box program which typified the American wartime machinery, and he thought you could simply wave a magic wand and POOF!” Mr. Eggers told investigators.

When discussing the state of the war in 2009, Barnett Rubin, who served as the senior adviser to the American special representative for Afghanistan and Pakistan from 2009 to 2013, described the American strategy in much starker terms. “But we were doing” counterinsurgency “as colonial power,” he said in a 2017 interview. “Afghans knew this influx of funds wouldn’t last, and they wanted to make the best of the windfall without endangering themselves. It was a fantasy that we could do that.”

The Washington Post said the new document trove has a precedent in the Pentagon Papers, but also drew distinctions with that 7,000-page study of the Vietnam War, which was based on internal government documents kept secret until published in 1971 by The New York Times and The Post.

In contrast, The Post describes the new documents as drawn from interviews conducted between 2014 and 2018 that were used by the inspector general for Afghanistan reconstruction to write a series of unclassified “Lessons Learned” reports that have been publicly released. “About 30 of the interview records are transcribed, word-for-word accounts,” The Post said. “The rest are typed summaries of conversations: pages of notes and quotes from people with different vantage points in the conflict, from provincial outposts to the highest circles of power.”

Since 2001, more than 2,200 American troops have been killed in Afghanistan, along with hundreds from allied countries that have contributed forces to the war. Since 2014, after the Pentagon officially and euphemistically ended “combat operations,” putting the Afghan military in the lead, more than 50,000 Afghan security forces have died. And the military effort has cost the United States more than $1 trillion.

Of the $133 billion that the United States has spent on reconstruction programs in Afghanistan, about $83 billion went toward training the Afghan Army and police forces, according to the inspector general.