People here need a history lesson, so here it is:
IS/ISIL/ISIS is the successor to an organization known as ISI in Iraq, which is in turn the successor of the organization known as Al Qaeda in Iraq - AQI.
This group traces to 2004 under the leadership of Al Zarqawi, a militant Islamist from Jordan. Zarqawi had gone to Afghanistan too late in 1989 to fight the Soviets, became friends with bin Laden and started a paramilitary Islamist group there to take over Jordan. Arrested and imprisoned several years in Jordan, he was released and went to Afghanistan, started a paramilitary training camp in 1999 with money from bin Laden and mostly fighters from Syria, Palestine, and Lebanon, but it had been disbanded or scattered before the US-led invasion. After another arrest and release in Jordan, Zarqawi returned to Afghanistan to fight against the invasion. Injured, he went for treatment to Iran.
Zarqawi went to Iraq in late 2001 or 2002. There, he plotted the assassination of a US diplomat in Jordan and bombings and trained forces in planning poison attacks. In 2004, he founded AQI - basically, his group there sought to be AQ in Iraq and this was okayed by bin Laden, but it remained an independent branch.
Though Zarqawi was killed in 2006, AQI continued. From 2003-2011, it joined with other Sunni insurgents. They formed a council later called Islamic State of Iraq - ISI - and drew support in various Sunni areas, because Sunnis resented the new power of Kurds and Shiites supported by the US. However, a backlash against their violence started to weaken their influence somewhat even before Zarqawi died.
Leadership of AQI passed to Al Baghdadi, a Sunni Iraqi with a doctorate in Islamic studies from Iraq’s main university, a pre-invasion cleric who had been a civilian internee of the US forces in 2004. After his release, he helped found a militant group that joined the council in 2006. He rose in the ISI and became top leader by 2010.
ISI expanded into Syria and announced its new name of ISIL in 2013. Al Bagdadhi claimed that the Al Nusra Front in the Syrian civil war, also an Al Qaeda branch, was an extension of ISI in Syria and would now merge into ISIL, but its leader objected and Al Zawahiri, now leader of Al Qaeda, also objected and said ISI should stick to Iraq. Al Baghdadi ignored this and managed to take control of about 80% of Al Nusra’s foreign fighters. By February of 2014, AQ under Al Zawahiri cut all ties to ISI/ISIL, though the ties had never been strong because AQ had long disapproved of ISI extremism (!).
Meanwhile, it has been claimed that foreign Al Nusra fighters were not the only rebels in Syria that had joined ISIL. It has been claimed that, in 2012, US forces vetted a small group of non-AQ rebels against Assad, secretly trained in Jordan, and sent them back to Syria armed to fight, but that they subsequently joined ISIL (!). In effect, what Obama had claimed from the beginning about Syria was apparently true - it’s just too difficult to be sure that, even with thorough vetting, giving arms to rebels in Syria is really arming the “good guys.”
Thus, the groups that morphed into ISIL/ISIS/IS preexisted Obama’s presidency, AQI was founded only after the US invasion of Iraq and partly in response to that invasion and absorbed disaffected Sunni insurgents. Moreover, AQI had had an aim to take over Jordan in the past of Al Zarqawi, and Al Baghdadi obviously saw that the vision of a greater Islamic state that could be brought about opportunistically by exploiting the Syrian civil war.
So actual problem traces back perhaps as far as the fight against the Soviets in Afghanistan under Reagan or Zarkawi’s AQ-funded terrorist training camp in the year 2000, the last year of Clinton’s term - at the end of which Clinton tried to offer Bush warnings and advice that were rebuffed. It became serious only in response to Bush’s Iraq invasion, after which it was an endemic problem exacerbated by the fact that it was impossible for us to fix Syria.
It’s worth noting that McCain was beating the drums for war with Iran in 2008, and AQI had wanted to incite such a war for several years to get the US off its back, and again that McCain was beating the drums for support for Syrian rebel groups early on, and the claimed attempt to support them apparently came to help the group into which AQI in the end.
If the GOP just stopped blaming our decent president and made it possible to collaborate on stopping the actual enemy of the US, humanity, and stability in the Middle East, our government might be able to accomplish that aim.
Much of the information above can be found by reading wikis on ISIL, the groups that morphed into it, and Al Zarkawi and Al Baghdadi, so please give credit to them - I don’t mean to be a plagiarist.