It was — so far — a spectacularly effective effort to establish deterrence on Trump’s part. There are two ways this happened. One had to do with the elimination of the specific threat posed by Soleimani.
A senior diplomat told me intelligence reports suggested that Soleimani was the most radical of the Iranian leaders, the one who pushed the hardest for the most extreme actions. If so, his departure from the scene silences a powerful confrontational voice at the Iranian table — and thus the killing was a deterrent act in itself.
It may be true that if you kill one terrorist mastermind, another will rise in his place. But the fact is that masterminds like Soleimani do not grow on trees. If you think of him as the Steve Jobs of state-sponsored terror, then it seems plausible to likely that he will be followed by a less creative type — the Tim Cook of terror, say.