When Robert Gates, US defence secretary, unexpectedly ousted his top US commander in Afghanistan this week, the rare move underscored the ongoing Pentagon shift from conventional warfare to counter-insurgency operations.

In the most dramatic dismissal of a wartime commanding general President Harry Truman fired General Douglas McArthur in 1951, Mr Gates announced his intention to replace General David McKiernan, the commander of US and Nato forces, just one year into his two-year tour in Afghanistan.