ISIS and IRAQ in a nutshell.

Here are five things to understand about ISIS and its fight across the Middle East:

• Who They Are: ISIS stands for Islamic State of Iraq and Syria, also known as the Islamic State of Iraq and the Levant (ISIL). The group is trying to form an independent state with territory in Iraq, Syria, and parts of Lebanon. They are led by an Iraqi cleric who goes by the name Abu Bakr al-Baghdadi.
• What They Do: ISIS has been fighting against Syrian President Bashar al-Assad as well as other militant Islamic groups in Syria for control of parts of Syria while also fighting the Iraqi government in its quest to form the unified ISIS state. Its brutal tactics have been disavowed as too extreme by al Qaeda's leader Ayman al-Zawahiri.
• How Powerful They Are: This week, ISIS forces took Mosul, the third biggest city in Iraq and the biggest one along the Iraq-Syria border. When they took the city, the ISIS seized more than $400 million from city banks, making it richer than many small nations. According to the Associated Press ISIS has also taken effective control of Tikrit, where Saddam Hussein was born.
• How They're Able to Fight: Since it controls cities on either side of the Syria-Iraq border, ISIS forces were able to quickly move weapons seized from Mosul into Syria on Monday. The weapons, including Humvees, rifles, missiles and ammunition, will help arm ISIS in its fights on both sides of the border.
• The State They Want to Create: The territory in the western part of Iraq that ISIS wants is made up of mostly Sunni Muslims, as is the part of Syria that ISIS wants. Many Sunni Muslims in Iraq have joined ISIS in fighting against the Iraqi Army, which is under the control of a Shiite minority that mainly lives on the other side of the country. 

Remember this?

If you believe Iraq was stable, I have a bridge to sell you.
Some Sunni groups (The Awakening) decided to kill some Al Queda folks and buy some time waiting for us to leave. They figured that put them in a better position to exert pressure on the government. It didn't work and so many teamed up with ISIS. In a few months or a year, they will split and start fighting one another.
Such is the way. It's power politics between factions. Once a civil war starts in the Middle East, alliances form, fray, reform, etc. etc.
There was never peace or stability, just strategic retrenchment. Somehow the same logic that made us think we could go in and establish a model democracy made us think there was peace and stability while various sides paused to regroup before the next bloodletting.