A confidential trove of government documents obtained by The Washington Post reveals that senior U.S. officials failed to tell the truth about the war in Afghanistan throughout the 18-year campaign, making rosy pronouncements they knew to be false and hiding unmistakable evidence the war had become unwinnable.

The documents were generated by a federal project examining the root failures of the longest armed conflict in U.S. history. They include more than 2,000 pages of previously unpublished notes of interviews with people who played a direct role in the war, from generals and diplomats to aid workers and Afghan officials.