“The military felt a sense of urgency, seeing little remaining time if any forces approved were to reach Afghanistan in time to improve security in advance of the elections,” he wrote.

The White House later approved the 4,000 troops, but the dispute pointed to a deeper clash of cultures over the use of force that continued after General McChrystal took command.

“Military leaders, many of whom were students of counterinsurgency, recognized the dangers of an incremental escalation, and the historical lesson that ‘trailing’ an insurgency typically condemned counterinsurgents to failure,” he writes.

In May 2009, soon before he assumed command in Kabul, General McChrystal had a “short, but cordial” meeting with Mr. Obama at which the president “offered no specific guidance,” he notes.