WASHINGTON -- Jeb Bush isn't even an official presidential candidate yet, but he's already facing a serious challenge to his candidacy -- and it just got worse because of a 19-year-old.

"Your brother created ISIS ," college student Ivy Ziedrich told Bush during a town-hall-style meeting in Reno, Nevada, on Wednesday. "ISIS" is a common name for the militant group that calls itself the Islamic State, and the "brother" in question, of course, is former President George W. Bush.

Moments earlier, the former Florida governor had been telling the audience that President Barack Obama was responsible for the rise of the militant group. But Ziedrich, a student at the University of Nevada, Reno, replied that Bush's version of history glossed over a few key events.

"You stated that ISIS was created because we don't have enough presence and we've been pulling out of the Middle East," she said . "However, the threat of ISIS was created by the Iraqi coalition authority, which ousted the entire government of Iraq. It was when 30,000 individuals who are part of the Iraqi military were forced out. They had no employment, they had no income, yet they were left with access to all the same arms and weapons."

Ziedrich's rebuttal to Bush came at a moment when the likely candidate was already facing questions over an earlier statement that appeared to suggest he supported the invasion of Iraq. (Bush walked back those comments Thursday, saying that "knowing what we know now," he would not have invaded the country.) And while Bush might not like to admit it, the truth is that Ziedrich's comments capture a point that has long been emphasized by Middle East watchers -- namely, that the Bush administration's mismanagement of Iraq encouraged thousands of skilled Iraqis to take their expertise to the anti-American insurgency that eventually became the Islamic State.

Jeb Bush and other Republicans have accused Obama of enabling the insurgency by withdrawing U.S. troops from Iraq at the end of 2011. The administration says it could not have maintained the troops there without an agreement to protect them that Baghdad was not at the time willing to sign.

But Bush's preferred reading of history overlooks the fact that the risk of an Islamic State-level militant expansion was clear back in 2003, after George W. Bush had ordered a U.S. invasion of Iraq on the basis of sketchy evidence. Saddam Hussein had at that point effectively controlled Iraq for more than 30 years . First tasting great power as the country's intelligence and internal security chief, Hussein invested heavily in making Iraq a police state, with loyal, well-trained agents of his Baath Party government as numerous in the country as conspiracy theories about their activities. He also focused on making his army a formidable force, appointing Sunni Arabs -- members of his own sect of Islam and a minority in Iraq -- to leadership positions. Hussein's rule forced those soldiers and officials to become even closer to the despot, because they, like many other people in the centralized quasi-socialist state that was Iraq, were reliant on government salaries, subsidies and favor.

Then an American came to Baghdad and told all those well-trained, well-armed men that their services would no longer be required. Or allowed.

Just over 12 years ago, George W. Bush appointed L. Paul Bremer to run Iraq. Bremer was given massive powers and a mandate to turn Iraq into a GOP dream: a free-market-loving, America-backing Muslim state that would stand as a shining beacon in the Middle East.

Bremer quietly left the country 14 months later, handing over power to an interim government in which 85 percent of Iraqis , at the time, said they lacked confidence. Much of their discontent had to do with Iraq's security problems, which U.S. officials told The Washington Post were exacerbated by Bremer's decision to disband the Iraqi army.

One of the men who lost his job was, according to a major recent report by the German magazine Der Spiegel, a key architect of the Islamic State.

Der Spiegel last month published a story based on captured documents that appear to belong to the Islamic State. Those documents discuss a man known to the militants as Haji Bakr. His real name -- the name by which he was known when he served in Saddam Hussein's air force intelligence services -- was Samir Abd Muhammad al-Khlifawi.

Der Spiegel spoke about Bakr with Iraqi researcher Hisham al-Hashimi, who has advised the Iraqi government. Hashimi said that Bremer's move left the onetime Hussein loyalist "bitter and unemployed."

The report continues:

Thousands of well-trained Sunni officers were robbed of their livelihood with the stroke of a pen. In doing so, America created its most bitter and intelligent enemies. Bakr went underground and met Abu Musab al-Zarqawi in Anbar Province in western Iraq. Zarqawi, a Jordanian by birth, had previously run a training camp for international terrorist pilgrims in Afghanistan. Starting in 2003, he gained global notoriety as the mastermind of attacks against the United Nations, US troops and Shiite Muslims. He was even too radical for former Al-Qaida leader Osama bin Laden. Zarqawi died in a US air strike in 2006.

Although Iraq's dominant Baath Party was secular, the two systems ultimately shared a conviction that control over the masses should lie in the hands of a small elite that should not be answerable to anyone -- because it ruled in the name of a grand plan, legitimized by either God or the glory of Arab history. The secret of IS' success lies in the combination of opposites, the fanatical beliefs of one group and the strategic calculations of the other.

Bakr, a top adviser to Islamic State leader Abu Bakr al-Baghdadi, died in 2014 . By that point, according to Der Spiegel's story and an analysis of Islamic State comments by The Long War Journal , Bakr had firmly established Baghdadi's pre-eminence within the group, helped the militants take over key towns in Syria and played a major role in the group's split from the central al Qaeda leadership in Pakistan and the al Qaeda affiliate in Syria. That last move was central to the Islamic State's claim to statehood and global leadership over Muslims. It is also thought to have enhanced the group's prestige among radicalized youth from around the world, thus making it more attractive to potential recruits.

A Washington Post report from last month confirmed the importance of former Hussein figures like Bakr in the overall Islamic State structure.

"Even with the influx of thousands of foreign fighters, almost all of the leaders of the Islamic State are former Iraqi officers, including the members of its shadowy military and security committees, and the majority of its emirs and princes, according to Iraqis, Syrians and analysts who study the group," the Post reported .

Much as Jeb Bush might dislike the legacy of his brother's policies in Iraq, it will be difficult for him to pretend it doesn't exist. It's one thing to say that he would not repeat the invasion, and another to acknowledge that the decisions made after the invasion have at least as much to do with the rise of the Islamic State as anything Obama later did. The question for Bush now will be how to account for that legacy, because it seems unlikely that Ziedrich will be the last person to bring it up.

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