• Send ground combat forces. Despite U.S. efforts to retrain them, the Iraqi army is now unable or unwilling to stand and fight ISIS alone. Its commanders have shamefully thrown down their weapons, discarded their uniforms, and abandoned their men and posts when ISIS threatens. The Iraqi army needs a backbone transplant.

U.S. airborne units can arrive quickly to secure Baghdad’s airport and the long and vital road from the city to that airfield. More Marines can better defend the U.S. Embassy in Baghdad. Americans can stiffen Iraqi lines around the city, and provide artillery and engineer units needed in urban combat. U.S. cavalry units can launch what imperial Britain called “punitive expeditions” to destroy ISIS lairs further afield.

The arrival of thousands more American fighting men will improve the Iraqi army’s performance. It was no accident that the Sunni Awakening and U.S. surge succeeded at the same time in 2006-07. As U.S. troops poured in, Sunni sheiks cast their lot with what Bing West memorialized as the “The Strongest Tribe” in his book of the same name.

There are natural advantages to defending Baghdad, which the Iraqis can exploit if steeled by U.S. troops. To seize the capital, ISIS’s lines of communication would expand, a logistical challenge that would leave them more vulnerable to counterattack. The Iraqi army’s lines of communication would helpfully contract.