The strike may have been a "target of opportunity" but it clearly had presidential authorisation for longer than just last night. The US clearly wants to send the signal that this is deliberate. But it is escalatory and brings the region to a new brink of unpredictable chaos. So how could they possibly calculate this was a good idea?
Well, Iran has been attacking the US and its allies via proxies for months. They are accused of hitting Saudi oilfields. A US drone before that. Oil tankers in the Gulf. And this week they directed attacks at the US Embassy in Baghdad, the US says.
The US is already being attacked by pro-Iranian forces, their officials could argue, so the US logic might be that any response from Iran will be a worsening of the same asymmetrical paper cuts already being inflicted.
It is true to note that Iran does not have the military might to tackle the US in an open conventional war. US officials may argue that they needed to send a strong signal that this White House was not gun-shy and would fight violence with violence, regardless of any denials from Tehran.
They may have decided the strength of this signal of US resolve, and removing the hardliner's hardliner Soleimani from the equation, was worth the risk of the next weeks of chaos and retaliation.
But like with all strategies there is a flaw. The Iranians have a plan. They had one for Iraq, where they continue to have influence despite protests, whereas the US doesn't really. They have one for Syria, from which the US keeps wanting to withdraw. They have proxies in Yemen, Lebanon, Syria, all able to extract a price from American allies. They can also extract a price from Israel, where Lebanon's Hezbollah has rockets aimed towards this key US ally, and a direct line to Iran. Iran is strategic, and it is patient.
Iran is also facing a White House where key personnel change annually. There is little Iranian expertise around President Donald Trump at this moment -- key officials often chosen simply for their hardline stance.
Brian Hook, Trump's Iran point man, has limited experience in this -- his only issue.
There is a wealth of expertise in the State Department and other agencies, but their morale is surely not at its peak after recent cuts and turmoil.
So we are left with an emphatic and game-changing signal from the US, made with the belief that the consequences will be unknowable, but probably manageable. One certainty will be that Tehran will seek to exact a price in a way that shatters that belief.