Retired Army Gen. Stanley McChrystal had a chance to kill the head of Iranian intelligence 12 years ago but passed on the opportunity because he feared, in part, "the contentious politics" that would have taken place after the incident.

McChrystal wrote a piece for Foreign Policy to discuss his decision and talk about the leadership skills that took Qassem Suleimani from a 22-year-old soldier to a major general leading the Quds Force within the Islamic Revolutionary Guard Corps — however sinister he may be.

"There was good reason to eliminate Suleimani," McChrystal wrote. "At the time [in 2007], Iranian-made roadside bombs built and deployed at his command were claiming the lives of U.S. troops across Iraq.

"But to avoid a firefight, and the contentious politics that would follow, I decided that we should monitor the caravan, not strike immediately. By the time the convoy had reached Erbil, Suleimani had slipped away into the darkness."

McChrystal, who was in charge of the Joint Special Operations Command from 2003-2008 and led both U.S. and NATO military forces in Afghanistan from 2009-2010, then wrote about Suleimani's rise to the top of the Middle East food chain.

"Suleimani has grown from a military commander into a ghostly puppet master, relying on quiet cleverness and grit to bolster Iran's international influence," McChrystal wrote. "His brilliance, effectiveness, and commitment to his country have been revered by his allies and denounced by his critics in equal measure.

"What all seem to agree on, however, is that the humble leader's steady hand has helped guide Iranian foreign policy for decades — and there is no denying his successes on the battlefield. Suleimani is arguably the most powerful and unconstrained actor in the Middle East today. U.S. defense officials have reported that Suleimani is running the Syrian civil war (via Iran's local proxies) all on his own."

McChrystal noted that in the United States, military leaders do not serve at the highest level for as long as Suleimani has in Iran. And that, he said, is a good thing.

"A zealous and action-oriented mindset, if unchecked, can be used as a force for good — but if harnessed to the wrong interests or values, the consequences can be dire," he wrote. "Suleimani is singularly dangerous. He is also singularly positioned to shape the future of the Middle East."