The U.S. Army War College revoked Democratic Sen. John Walsh's master's degree after an investigation completed Friday concluded he plagiarized a research paper required to graduate, a college spokeswoman said.

The Carlisle, Pennsylvania, college assigned an academic review board to the probe in August after The New York Times published a story showing Walsh borrowed heavily from other sources for the paper he wrote in 2007.

Walsh was pursuing a Master of Strategic Studies degree at age 47, a year before he became Montana's adjutant general overseeing the state National Guard.

The board took less than a day to hear the case and make its findings Aug. 22, but the process of appeal and review wasn't completed until Friday.

"The board found that then Colonel John Walsh did commit the offense of plagiarism and thus his Master's Degree and status as graduate of the U.S. Army War College should be revoked," War College spokeswoman Carol Kerr said in a statement.

The review board made its conclusions less than 20 minutes after closing its August hearing, according to the report released by Walsh's office. Possible extenuating circumstances submitted by Walsh of post-traumatic stress disorder and a fellow soldier's suicide were not enough to support any other recommendation.

"It should also be noted that other students ... have had similar or more serious personal and psychological issues during their year at USAWC, and they have been able to successfully complete course requirements without resorting to plagiarism or other cheating," the review board's report said.

Walsh's office released a statement saying the senator disagrees with the findings but accepts the college's decision.

"I apologize to all Montanans for the plagiarism in my 2007 paper, and I am prepared to live with its consequences," Walsh said in the statement. "I may not be a scholar, but I am proud to have been a soldier who has served Montana and this great nation for 33 years in uniform."

His spokeswoman said he was not available for further comment.

Walsh dropped out of the Nov. 4 Senate race after the plagiarism. He was appointed to his Senate seat in February when Max Baucus resigned to become ambassador to China.

In August, Montana Democrats chose state lawmaker Amanda Curtis to replace Wash as their candidate.

Republicans need a net gain of six seats in November to take Senate control, and Montana is a prime target to pick up a seat that's been in Democratic hands for more than a century.

The Senate race was seen as a tough one for Democrats even with the incumbent Walsh in the running. Now Daines is expected to have a bigger advantage going against a newcomer who doesn't have his name recognition or $1.7 million campaign bank account.