If Obama questioned military generals as Gates' alleges, that was a good thing. Having doubts about Afghanistan is a plus rather than a negative. I don't see "Duty" as a staggering blow. Here is commentary from someone who worked with Gates.

From the horse's mouth:

Gates Says His Points About Obama Have Been Mischaracterized
By Mark Memmott, The Two Way @ npr.org, Jan. 10, 2014

Your initial news post by Melvin Goodman was very interesting because he is someone who knows Gates well. Note he very much was respectful of the fact that he hasn't read the book and was just trying to offer his opinion about Gates to those thinking of reading the book.

But in mho, this Consortium News piece by Robert Parry is just speculative crap by someone who didn't read the book, with an inflammatory description of it as "back stabbing," a characterization which isn't shaping up to be very accurate at all.

US 'tried to oust Hamid Karzai by manipulating Afghan elections'
Former defence secretary Robert Gates is quoted as saying in his memoirs that US tried to eject Afghan president in 2009
By Emma Graham-Harrison, theguardian.com, 10 Jan. 2014   

[....] The Afghan election, eventually held in August 2009, was marred by widespread fraud and badly damaged Karzai's international reputation, but Gates laments that the US too was stained by underhand efforts to control the result.

"It was all ugly: our partner, the president of Afghanistan, was tainted, and our hands were dirty as well," Gates wrote. "Our future dealings with Karzai, always hugely problematic, and his criticisms of us, are at least more understandable in the context of our clumsy and failed putsch."

Senior diplomat Richard Holbrooke, then special envoy for Afghanistan and Pakistan, paid public lip-service to the idea of a level playing field, but was working behind the scenes to ensure the opposite, Gates said. He first supported an unconstitutional three-month delay to the election and then, with the help of the US ambassador in Kabul, Karl Eikenberry, backed Karzai's rivals, he alleged. Holbrooke aimed to push the poll to a second round that the incumbent would lose, but the candidate who got through cancelled the vote and conceded to Karzai.

"Holbrooke was doing his best to bring about the defeat of Karzai," Gates writes. "What he really wanted was to have enough credible candidates running to deny Karzai a majority in the election, thus forcing a runoff in which he could be defeated."

Tactics included advising candidates, attending rallies and organising high-profile photo opportunities, according to Gates, who is highly critical of Karzai elsewhere in the book.

He ponders if the president "listened to anyone but the conspiracy-minded", but points out that the Afghan leader could not have missed what Holbrooke was doing. "Karzai might not be a great president, but he sure as hell knew what was going on in his own capital and was well aware of the American efforts to unseat him," adds Gates.

A spokeswoman for the US National Security Council said Gates's account was untrue. "I worked for Ambassador Eikenberry at the time, watched all of this up close and personal, and that's just categorically false," Caitlin Hayden said in an email response [....]