The ghost of Abu Musab al-Zarqawi, the founder of what is today the Islamic State of Iraq and al-Sham (ISIS) has become the next generation of "al-Qaedism" — more violent, ruthless and extreme than any of its predecessors. ISIS made a bold gamble for its stunning victory in Mosul, taking both a historic great city and symbolic leadership of the global jihad.

Zarqawi, a nom de guerre, was the Jordanian gangster who created al-Qaeda in Iraq, the base from which ISIS evolved, to fight the US invasion. He started from scratch in 2002 even before the invasion began, since then-President George W. Bush made his plans known well in advance of the war. Zarqawi set a trap and built cells ready to strike after the invasion. Then Zarqawi plunged the country into civil war and through his extreme violence persuaded most of Washington that the war was a bad mistake. Although he died in 2006, his legacy survives. 

Late al-Qaeda leader Osama bin Laden was always suspicious of his Jordanian protege even before Sept. 11, 2001, and sought to keep him at arm's length. Bin Laden exiled Zarqawi for a time to western Afghanistan because he distrusted Zarqawi's loyalty and his extreme sectarian violence against Iraq's Shiites. But he valued Zarqawi's efficiency once the Iraq war started. 

The Bush surge in 2007 did not destroy Zarqawi's empire. A residual US ground force would not have eliminated it, either. Decapitating the group and buying the Sunni tribes only forced it deeper into the angry Sunni underground. Only sustained good and smart governance could kill it, and that was something post-Saddam Hussein Iraq could not produce, with or without the United States.