This week, The Washington Post released a collection of over 2,000 pages of notes from interviews with more than 400 officials directly involved in the war in Afghanistan.

They paint a grim picture of how officials kept reassuring the public of progress while privately harboring doubts about their mission and its chances of success.

Retired Army Lt. Gen. Dan McNeill, who served as the commander of US and coalition forces in Afghanistan, told interviewers that "nobody could" explain to him "what winning meant."

Visit Business Insider's homepage for more stories.

The US has been fighting in Afghanistan with no clear strategy for nearly two decades, a collection of documents obtained by The Washington Post reveal.

"I tried to get someone to define for me what winning meant, even before I went over, and nobody could," retired Army Lt. Gen. Dan McNeill, who served as the commander of American and coalition forces in Afghanistan told US government interviewers, the documents show.

"Nobody would give me a good definition of what it meant," added McNeill, who commanded US troops in Afghanistan in 2002 and 2003, and the NATO coalition in 2007 and 2008.

The Post's "Afghanistan Papers," a collection of over 2,000 pages of notes from interviews with more than 400 people directly involved in the war in Afghanistan, paint a grim picture of how officials kept reassuring the public of progress while privately harboring doubts about their mission and its chances of success — confirming what many observers have suspected for years.

Not only did the US and its partners have an undefined mission, but it also lacked a sufficient understanding of the Afghanistan. As a result, the US sacrificed thousands of lives and wasted nearly a trillion dollars trying to stabilize a country that remains unstable today, The Post reports.

Suicide bombers struck the main US military base — Bagram Air Base — in Afghanistan Wednesday, killing one person and injuring dozens of others. The Taliban, the Islamist insurgent force with which the US is trying to achieve a negotiated peace, claimed responsibility for the attack.

Asked about the "Afghanistan Papers" Wednesday, Secretary of Defense Mark Esper simply said he hasn't read all of them and is focused on moving "forward."

The Pentagon has been largely unwilling to discuss the 18-year war in Afghanistan, America's longest armed conflict.

Gen. Austin Miller, the current commander of US forces in Afghanistan, will brief lawmakers Wednesday afternoon in a hearing closed to the public; there are no plans to discuss the war publicly, despite repeated requests from defense reporters.

"There has been no intent by DoD to mislead Congress or the public," a Pentagon spokesman said in an emailed statement earlier this week after the Washington Post articles published. "DoD has been very clear that this war will not end on the battlefield."

The spokesman added that "our military mission in Afghanistan is in support of diplomatic efforts to achieve a peace settlement."