The Washington Post has published a report based on a confidential cache of U.S. government documents showing that three White House administrations misled the public about shortcomings and failures in the 18-year Afghanistan war.

They reveal that the war, in which 2,300 U.S. soldiers have been killed and nearly $1 trillion has been spent, has become unwinnable.

The trove of documents, which include more than 2,000 pages of notes of interviews with people who played a direct role in the war, lay bare 'pent-up complaints, frustrations and confessions, along with second-guessing and backbiting,' The Washington Post reported.

Some 400 insiders offered criticism spanning Washington's ever-changing strategy in Afghanistan, shortcomings in developing an effective Afghan fighting force, failures to defeat the Taliban, and fighting corruption throughout the government.

'We were devoid of a fundamental understanding of Afghanistan -- we didn't know what we were doing,' Douglas Lute, a three-star army general who served as the White House's Afghan war leader during the Bush and Obama administrations, told government interviewers in 2015.

The interviews were part of a project by the Special Inspector General for Afghanistan Reconstruction (SIGAR) over the past several years.

'U.S. official acknowledged that their warfighting strategies were fatally flawed and that Washington wasted enormous sums of money traying to remake Afghanistan into a modern nation,' The Washington Post reported.

No comprehensive U.S. government accounting of war spending has been conducted.

Between $938 billion and $978 billion has been spent since 2001 on Afghanistan by the Defense Department, State Department, and U.S. Agency for International Development, according to Neta Crawford, a political-science professor and co-director of the Costs of War Project at Brown University.

The calculation doesn't include money spent by other agencies, such as the Central Intelligence Agency or the Department of Veterans Affairs.

In addition, some of those interviewed said statistics at the military headquarters in Kabul and the White house were distorted to give the impression that the United States was winning the war.

With reporting by The Wall Street Journal, AP, and The Washington Post

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