Peter Bergen is CNN's national security analyst, a vice president at New America and professor at the School of Politics and Global Studies at Arizona State University. He is the author of "United States of Jihad: Investigating America's Homegrown Terrorists." The opinions expressed in this commentary are his own. View more opinion articles at CNN. This article has been updated to reflect the latest news.

(CNN) At the last possible minute President Trump did something smart on Iran Thursday night: He pulled back strikes on three Iranian targets that could have killed as many as 150 people because, he tweeted, it wasn't a "proportionate" response to Iran bringing down an unarmed US drone.

Indeed, that is a good reason.

There are also other good reasons. First, it is Congress that is supposed to authorize American wars. Such a potentially lethal strike surely would need, at an absolute minimum, congressional buy-in, and more properly it would need an actual congressional resolution for the use of force. US presidents have sometimes disputed Congress's authority over military strikes, but congressional approval is how things should work, according to the War Powers Resolution of 1973.

Second, an escalatory strike of this scale could pose serious risks to Americans in the Middle East. Unlike the Syrian regime against which Trump launched air strikes in 2017 and 2018, Iran has the capacity to launch significant retaliatory operations across the Middle East. Iran and its proxies have major presences in Lebanon, Iraq, Syria and Yemen. Iran also has thousands of missiles with ranges of up to 1,500 miles that can hit targets around the region, including Israel, and can reach as far as southeastern Europe.

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The more hardline elements in Iran could easily unleash their forces or proxies against American troops in both Iraq and Syria or against American commercial targets around the Middle East.

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