Assassinating Soleimani is a justified act, but it takes place within the context of a largely unjust and strategically indefensible grand strategy, so it is unlikely to be a net positive in the long run. Let me explain:
Soleimani was a terrorist. The fact that he wore an Iranian uniform only make Iran complicit with his terrorism; it does not shield him from culpability for the terrorism committed by the IRGC-Qods Force or the many militias under his command and influence.
Iran, or at leas the parts of the Iranian govt that Soleimani worked in, has been waging war on the United States for over a decade. Responding in kind to Iran's aggression was well within our rights and long overdue.
But....
But....
Just war aims at peace, not at a never-ending escalating spiral of tit-for-tat violence. Is there any evidence that the US intends anything other than a never-ending escalating spiral of tit-for-tat violence here? Any evidence that we have a plan for peace?
Look at US strategy in the region at least since 2011. We whack terrorists with impunity and ignore the conditions that give rise to terrorism. That's not just stupid. That's unjust. We help perpetuate a state of war because it's too inconvenient to work for peace.
People complain about "endless wars," which I think is usually an intellectually lazy bad-faith argument. But we literally have a policy of endless war against terrorists (including the proxies that Soleimani supported) because we have no plan to actually win and end the wars.
A just grand strategy looks towards peace and justice. If that means assassinating a state sponsor of terrorism (which, again, it can), it also must mean embedding that assassination within a set of policies that collectively move towards peace and justice.
That probably should include: a public declaration of our aims and of our demands against Iran, an offer of talks to deescalate, a massive increase to our reconstruction and stabilization operations in Iraq, some coherence to our policy in Syria...
...efforts to educate the American people and world opinion, rally support, and prepare for a longer fight; outreach to Allies; conducting public diplomacy to publicize Iran's crimes, denigrate the ideology that leads to their terrorism, champion a viable alternative, etc etc.
In other words, playing whack-a-mole with bad guys is not, by itself, an effective or defensible strategy, but I see little evidence that we're even trying to do anything other than that.
