Updated

The roughly 300,000 refugees from Syria, Iraq, Afghanistan and other Middle East countries pouring into Europe this year is sparking new questions about the extent to which U.S. foreign policy under then-Secretary of State Hillary Clinton has contributed to the crisis.

Critics of Obama administration policy while Clinton was the country’s top diplomat argue in large part that she and President Obama failed to keep U.S. troops in Iraq after December 2011, creating a void for the Islamic State to form and embark on a reign of terror that has killed and displace tens of thousands in the Middle East just over the past few years.

“That premature withdrawal was the fatal error, creating the void that ISIS moved in to fill and that Iran has exploited to the full as well,” former Florida Republican Gov. Jeb Bush, who is competing with the Democrat Clinton to become president in 2016, said in early August.

“Where was the secretary of state in all of this? In all her record-setting travels, she stopped by Iraq exactly once,” he said. “Who can seriously argue that America and our friends are safer today than in 2009, when the president and Secretary Clinton … took office?”

Clinton hit back, arguing the administration of Bush’s brother, George W. Bush, established the troop-withdrawal date and that the Obama administration had to honor the date because then-Iraqi Prime Minister Nouri al Maliki rejected a proposed to keep several thousand U.S. troops in that country for training purposes.

“I find it somewhat curious that Jeb Bush is doubling down on defending his brother’s actions in Iraq,” Clinton responded. “But if he’s going to do that, he should present the entire picture. … The entire picture includes the agreement George W. Bush made with the Maliki government.”

Nowhere is the problem worse than in Syria, where a four-year civil war has displaced an estimated 7.6 million people and forced an additional 4 million into such neighboring countries and Turkey, Hungry, Lebanon, Jordan and now Western Europe.

The war is between the regime of President Bashar al Assad and rebel forces trying to oust the government, long accused of crimes against humanity.

Critics of U.S. foreign policy say Obama has allowed Assad to stay in power by in part not providing enough U.S. military assistance to rebel forces. And they argue Obama announced in August 2012 that Syria would cross a “red line” by using or moving around chemical weapons. However, they say, the president did nothing after evidenced showed in April 2013 that such weapons were used on the Syrian people.

Clinton was secretary of state from 2009 to 2013. And she has also been criticized about her role leading up to the Sept. 11, 2012, terror attacks in Benghazi, Libya, in which U.S. Ambassador Chris Steven and three other Americans were killed.

Critics argue that Clinton’s testimony before Congress and other evidence shows that she and others in the administration failed to provide adequate security at the U.S. outpost in Benghazi and that they underestimated the terror threat in the region.

Clinton is scheduled to testify again on the matter in October, before the GOP-led House’s Select Committee on Benghazi. And the United States has officially pulled out of country, whose internal fighting has further destabilized the region.

Critics also argue that Obama has underestimated ISIS, pointing to him suggesting last year that the terror group is a “jayvee” team. However, the Islamic State’s foray into Syria has helped turned the years-long refugee situation into a crisis.

“This spreading anarchy derives, in substantial part, from Barack Obama’s deliberate policy of ‘leading from behind’ by reducing U.S. attention to and involvement in the region,” John Bolton, a former U.S. ambassador to the United Nations and a Fox News contributor, recently said.

Yacoub El Hillo, the United Nations’ top humanitarian official, said in March that the impending crisis was “price of political failure,” according to The New York Times.

Clinton last year attempted to distance herself from some of the Obama administration's handling of the Arab uprisings in the Middle East.

In her book “Hard Choices,” Clinton writes that she pushed in 2011 for Egyptian President Hosni Mubarak to transition power to his successor but was overruled by Obama.

Clinton says she didn't want the U.S. to be seen as pushing out a longtime partner without a clear picture of the future for regional allies such as Israel and Jordan.

After Mubarak stepped down, violent street protests continued for several years and the Muslim Brotherhood-led government that came to power was ousted in a military coup.

The United States has already taken about 1,500 Syrian refuges, and the Obama administration said earlier this week that the country will try to do more next year, by perhaps taking in thousands more.

However, that effort will likely face some opposition from Washington Republicans and others concerned that ISIS terror agents could slip into the country.

The Associated Press contributed to this report.