The United States has killed Major General Qassem Soleimani, the commander of the Islamic Revolutionary Guard Corps’s Quds Force. The United States is now in a hot war with Iran after having waged war via proxies for the past several decades.

This doesn’t mean war, it will not lead to war, and it doesn’t risk war. None of that. It is war.

I don’t claim to be an expert on Iran—when I served as deputy assistant secretary of defense for Middle East policy, I used to remind my Iran team at the Pentagon that my regional expertise ended at the Shatt al-Arab waterway that divides Iraq and Iran, and with them, the Arabic- and Farsi-speaking regions of the Middle East.

But I do know something of how important Qassem Soleimani was, because he spent more time in the Arabic-speaking world—propping up Iranian allies from Iraq to Lebanon, and from Syria to Yemen—than he did back home in Iran. From a military and diplomatic perspective, Soleimani was Iran’s David Petraeus and Stan McChrystal and Brett McGurk all rolled into one.

And that’s now the problem Iran faces. I do not know of a single Iranian who was more indispensable to his government’s ambitions in the Middle East. From 2015 to 2017, when we were in the heat of the fighting against the Islamic State in both Syria and Iraq, I would watch Soleimani shuttle back and forth between Syria and Iraq. When the war to prop up Bashar al-Assad was going poorly, Soleimani would leave Iraq for Syria. And when Iranian-backed militias in Iraq began to struggle against the Islamic State, Soleimani would leave Syria for Iraq.