The terrorist group ISIS has risen in prominence during the last couple of years and, according to a former defense secretary, it's because of two main reasons.

According to Robert Gates, a former U.S. Defense Secretary to both President Obama and Bush, there are two main reasons why the Islamic State managed to rise, and contrary to popular belief, it's not exactly the U.S.'s fault.

During an interview with Business Insider, Gates said that the Syrian civil war and the policies of Iraq's former prime minister, Nouri al-Maliki, were the main reasons to blame for the rise of the Islamic State.

Gates said, "I think the primary reasons for the rise of ISIS are the Syrian civil war and the policies followed by the government in Baghdad."

"When we left, most of the leaders of the Iraqi Security Forces were people we'd had a hand in training, and in some cases selecting, and they were pretty capable people," Gates added.

Maliki then replaced all those leaders that the U.S. have trained with "incompetent and corrupt" people, and added that no Iraqi soldiers would fight for them.

He added that way before the war in Syria broke out five years ago, President Bashar al-Assad had permitted so-called secret routes that allowed jihadists to travel back and forth across the country's border with Iraq, which resulted into the insurgency in the country and resulted into ISIS.

However, he did acknowledge that the U.S. had a bit of involvement with its formation, but again, for different reasons. Gates argued that the U.S. troops should not have left Iraq back in 2011, due to the fact that they could have served as mediators in the conflict.

He said that back when the troops were in Baghdad, they had the ability to get the leaders of all the involved parties in the conflict, from the Sunnis, the Shias and the Kurds.

In addition, he also ripped both the Democrats and the Republicans regarding their proposed action for the terrorist group.

According to him, none of the candidates right now aspiring to run as president have the necessary qualities to be a great leader, The Hill has learned.

Gates also singled out Republican presidential candidate Ted Cruz's suggestion of carpet bombing the terrorist, and said that it would be ineffective and just harm innocent civilians.

For him, it's a total opposition to the "American Way" of things when it comes to war and said that Cruz's proposed course of action, only advocates total disregard for civilians.