I'll be honest, this one is difficult. As much as I would love to see the war in Afghanistan end, we need to withdraw correctly. Let's use Iraq as an example. First, look back to the 2003 U.S.-led invasion of Iraq. That, and the dismantling of the entire security force, created an angry, mainly Sunni demographic, which fueled the insurgency that would later become ISIS. On top of that, most Iraqis saw the U.S. soldiers as occupiers who were responsible for civilian deaths. With the influx of American soldiers, the U.S. military organized Sunni tribes to fight against insurgents. The Americans paid them, helped arm them and gave them air cover. One of those tribal leaders, Sheikh Hamid Taees, said: "In May of 2006, I worked closely with the American side to rid Anbar of terrorism and al Qaeda, and actually we killed a large number of al Qaeda fighters." But by the time of that comment, early in 2014, al Qaeda was beginning to get a grip on Sunni areas again, including that province of Anbar. Many Sunni sheikhs say once the American soldiers left, the minority Sunni population of Iraq suffered under a government dominated by the Shiite majority. That government stopped paying most of them, and even arrested many. In doing so, some Sunnis were drawn back to the insurgency. ISIS found supporters and gained ground. And, yes, much of that could have been prevented by a big U.S. troop presence. The other thing that happened after the American military left was that the Iraqi army deteriorated dramatically. "They really did become relatively complacent, and then flat out just didn't train," said Major-General Paul E. Funk II, speaking after abruptly returning to Iraq on a training mission 2014. "Just didn't spend the money to do it, didn't maintain the systems and therein lies the problem." And corruption was running rampant. Supplies were stolen and soldiers were paid, who never reported for duty. Another crucial thing is Syria. With the civil war in 2011, suddenly, just over Iraq's borders were vast ungoverned spaces and lots of weapons. It became a safe haven for ISIS to grow in. And, so, when ISIS came rushing into the city of Mosul, the military collapsed. ISIS had more men and bigger weapons. So, yes, the withdrawal of U.S. troops helped ISIS. If they'd stayed, they could have bolstered Iraq's security forces and tamped down Sunni anger. Afghanistan is no different. If we don’t learn from our mistakes, we are doomed to repeat them.