You couldn't call Admiral William Fallon a popular man in the White House, Pentagon or US Army, although his resignation this week may have made him more so. It would be hard to call him effective, as senior army officers kept sniping in private.

But he was right on crucial points of US strategy even if he was the wrong person to run US Central Command. On Iran he was outspoken — and right — about the need for engagement and the folly of a military strike. He was right that Iraq had sucked the United States' attention away from “the five or six pots boiling over” in the same part of the world. However, he was wrong on the surge in Iraq, and that, as well as personality clashes, is what probably did for him.

It was always going to be a tricky appointment — to take a navy officer and put him in charge of Centcom, which covers Iraq and Afghanistan and relies, more than any other command centre, on knowledge of combat operations. Fallon was the first navy appointment to the post, usually held by army generals with recent experience on the ground.

It would be wrong to explain the antagonism that his appointment provoked purely by inter-service rivalry, although even these days, when the fashion is to pretend that it no longer exists, the reflex runs deep. But his lack of direct experience of the two conflicts left him with no way to challenge General David Petraeus, President Bush's adored commander on the ground. Fallon's argument for drawing down US troops more quickly, while consistent with the thinking of some generals, dissolved in the face of Petraeus's case that the surge was working and that troop strength needed to be maintained.

But it was on Iran where Fallon clashed most with the White House, arguing openly against a strike and for persuasion. His departure does not make a strike more likely; he is hardly alone, among the Administration or senior military officers, in thinking that it could have uncontrollable effects. Nor, this time, would Britain consider joining the US. It would take a lot — more than Israel's encouragement — to make an attack an attractive option for the US.

But Fallon's sudden exit will be intently studied in Tehran, as is every clue about US intentions. It is in keeping with the past eight years of American policy towards Iran — confused, full of sound and fury, and most valuable simply in keeping Iran guessing.

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