By George Kenney 
The market for oil is a global market. Not perfectly homogenized, but global. So if the U.S. and Europe say that they plan to further "punish" Iran for its nuclear program by implementing a European boycott of Iranian oil or sanctions generally against those who buy Iranian oil, well, that's the proverbial paper tiger talking. To be sure, the Iranians understand. It was, then, a very serious mistake for Iran to threaten to retaliate by closing the Strait of Hormuz, not only because it was unnecessary but because the threat turned war from a negligible possibility (because self-evident direct costs are too great) into something much more tangible. Although Iranian Rear Admiral Mahmoud Mousavi walked back  the Iranian position on Sunday, Iran's Army Commander in Chief, Maj. General Ataollah Saleh i, further stoked  the dispute on Tuesday, saying  "We recommend to the U.S. warship [the USS John C. Stennis] that passed through the Strait of Hormuz and went to the Gulf of Oman not to return to the Persian Gulf... The Islamic Republic of Iran will not repeat its warning." Let's hope not. Going forward the Iranians would be extremely well advised never to say anything again about disrupting the West's oil supply.
Oil has not become a higher priority than nuclear proliferation, but an American decision to go to war can sometimes have less to do with principles or objective calculations than with the inertial momentum of a vast national security apparatus. Hit the right buttons and war pretty much automatically ensues.
During the first Gulf War (August 1990-February 1991) I was the desk officer for oil security, for oil consuming countries, at the State Department. What I remember most vividly about that war — apart from meetings of the IEA in Paris and having splendid bistro dinners with old friends — was how fast and how automatically we took the decision to use military force. Somewhat paradoxically, the decision had been years in the making through the national security inter-agency process. Having identified oil supply as a vital interest and having thus produced a number of presidential directives covering various disruption contingencies, when Saddam Hussein unexpectedly invaded and annexed Kuwait , instead of turning to fresh considerations regarding the utility or desirability of war the national security bureaucracy, as one, reached into its safe, dusted off the relevant directives, and clamored for a military solution. Given such riotous momentum even President George H.W. Bush — had he wanted — might not have been able to negotiate a peaceful outcome.
Although Secretary of State James Baker famously rationalized the first Gulf War as being about "jobs, jobs, jobs" the fact is, because of the world market, nothing about Iraq's invasion of Kuwait mattered to the U.S. economically (assuming Saddam Hussein would not have withheld Kuwaiti oil out of spite). If the White House had tried to logically think things through it might have been possible politically to downgrade the crisis into a vexing border dispute. But within government the automatic imperative of war went virtually unquestioned. 
To the extent that relevant presidential directives may have been revised between 1990 and today one assumes they must be even more robust. So the same automaticity in principle applies. Moreover, the imperative should be even greater today since in this case closing the Strait of Hormuz would, indeed, raise the world price of oil.  To be somewhat cynical another factor should be taken into account as well: Having left Iraq and having started drawing down in Afghanistan the U.S. military needs another expensive war in order to justify its huge budget.
Iran ought to be aware of all this. If the U.S. and Iran had had diplomatic relations during the past 30 odd years, it probably would be. But not having had diplomatic relations Iran evidently has trouble distinguishing between its (so far) successful finessing of the nuclear issue and what is, from Washington's perspective, a brilliant red flashing neon line.
It's worth noting that lots of third world countries make this sort of mistake. They assume that the U.S. knows what it's doing and they therefore ascribe all sorts of intentionality to what are, in reality, relatively random acts. 'The U.S. has not seriously pushed for war regarding nuclear proliferation, therefore the U.S. does not want war for any reason.' If only life were so simple. The Iranians clearly have no idea of the danger they have provoked. The situation thus resembles a classic case of two states slipping accidentally into a war neither wants. But who will explain  things to Tehran?
We may yet luck out. Iran may not actually do anything. Iranian officials may pipe down. President Barack Obama may prove a different kind of leader than George H.W. Bush. And unlike 1990, given the many false starts against Iran, a number of entrenched U.S. bureaucratic obstacles to war now exist. Repeated war games, for example, have raised awareness of potential costs, including a catastrophic collapse of the world economy. In 2012 that's no small worry. Nonetheless, if push came to shove the predetermined vital U.S. national security interest would most likely trump objections.
 Caught by surprise, until about a week to 10 days prior the consensus of U.S. intelligence estimates regarding what might happen was little more than a vague guess.
 I questioned the rationale for going to war but I was not a senior officer and nobody listened.
 Threats of oil supply disruptions also probably will bleed back into the proliferation stalemate, giving hawks new arguments against an Iranian acquisition of nuclear leverage.