Colin Powell’s recent intervention in the debate about the Bush administration’s proposal unilaterally to alter the Geneva Conventions marked a departure from the silence of the former secretary of state and ex-chairman of the joint chiefs of staff. Whether or not we hear more from General Powell in the years to come, we are likely to hear much more about his doctrine.

The “Powell doctrine” holds that the US should go to war only as a last resort and then only with overwhelming force. In his article “US Forces: Challenges Ahead” in Foreign Affairs in 1992-93, Mr Powell posed a number of questions to be asked by US policymakers before launching a war. Is a vital national security interest threatened? Do we have a clear, attainable objective? Have the risks and costs been fully and frankly analysed? Have all other non-violent policy means been exhausted? Is there a plausible exit strategy? Have the consequences been fully considered? Is the action supported by the American people? Does the US have broad international support? The Powell doctrine developed similar principles laid out by Caspar Weinberger, defence secretary during the Reagan administration. Mr Powell, like Mr Weinberger and much of the US military, was determined to avoid large-scale debacles such as the Vietnam war and minor disasters such as the Somalia intervention in 1992-93.