The attack marked a significant escalation in the confrontation between the US and Iran.
Britain is inevitably involved in this as America's only important foreign ally in Iraq. In fact the US raid could have had even more significant consequences if the Americans had captured the Iranian official they were targeting. Fuad Hussein, the chief of staff of the Kurdish president Massoud Barzani, told The Independent that "they were after Mohammed Jafari, the deputy chairman of Iran's National Security Council."
It is a measure of the difficulty America has in getting its close allies in Iraq, notably the Kurds, to join it in confronting Iran that Mr Jafari was in Arbil as part of an Iranian delegation. He had just visited Mr Barzani in his mountain-top headquarters at Salahudin and earlier he met with Iraqi President Jalal Talabani in Dokan in eastern Kurdistan.
The political links between Iran and Iraq will be difficult to sever. Most Iraqi political leaders, Arab or Kurdish, were exiles in Iran or in Syria. They are also conscious that one day the US will withdraw from Iraq but Iran will always be there.
Some businessmen in Arbil scent profitable opportunities as the UN tightens its embargo on trade with Iran, announced at the weekend by the UN. As official trade is squeezed, they foresee remunerative possibilities for smuggling goods in and out of Iran.
Economically, northern Iraq needs Iran more than Iran needs it. Iranian petrol commands a premium price because it is considered pure and Kurdistan is eager to increase its supply of electricity, of which it is permanently short, from Iran.
In terms of US domestic and international politics, an American confrontation with Iran on the nuclear issue probably makes sense. Washington can rally support against Iran in a way that it cannot do when it looks for support for its occupation of Iraq. Seeing the US bogged down in Iraq, the Iranians may have overplaying their hand in developing nuclear power.
Inside Iraq, confrontation with Iran does not make much political sense. All America's allies in Iraq have close ties with Iran. The only anti-Iranian community in Iraq is the five million Sunni who have been fighting the US for the past four years.
The US raid on Arbil in January would have had far more serious consequences if Mr Jafari had been abducted. As it was, the seizure of five Iranian officials seems to have set the scene for the Iranian Revolutionary Guards seizing 15 British sailors and marines.