Before Qassem Soleimani was killed in a US air strike in Iraq, he was arguably Iran's second most important leader. He commanded the soldiers and spies of Iran's elite Quds Force, a group whose job was to forge partnerships with militias across the Middle East, through which Soleimani spread Iran's influence and his own. From Hezbollah in Lebanon to the many Shia militias in Iraq, these groups played a central role in the medley of wars that have roiled the Middle East for the last few decades. Soleimani didn't invent Iran's use of proxy militias; that dates back to at least 1979, when Iran's new regime looked around the region and found many enemies and few friends. But 40 years later, thanks in part to Soleimani's work, Iran has the advantage in the Middle East.