The problem became worse when al-Qaeda elements in Iraq and Syria merged in April to form the Islamic State of Iraq and the Levant, which is known by the acronym ISIS. The group is believed to be one of the main jihadi groups fighting forces loyal to Syrian President Bashar Assad, and they have claimed responsibility for several attacks in Syria. According to David Siegel, an associate professor of political science at Duke University, in North Carolina, who studies the evolution of terrorist organizations, such a merger is unusual. “Typically, groups don’t join together,” Spiegel says. Smaller groups have assumed the mantle of al-Qaeda to give themselves more credibility, but “mergers that are actually real mergers are rare.” According to the BBC, two months after the ISIS merger was announced, al-Qaeda’s leader Ayman al-Zawahiri reportedly ordered the union negated.

Yet that hasn’t stopped ISIS from having a potentially enormous impact on violence in Iraq. Two weeks ago, reports emerged that the Iraqi government planned to form a “special division” in Baghdad composed of Shi‘ite militias to fight al-Qaeda, a charge al-Maliki’s government has denied. Such a division would likely consist of groups who played major roles in the 2006–07 sectarian bloodbath, and rearming those militias could rekindle a fiery era during which each morning brought the grisly sight of dead bodies along the edges of Sunni and Shi‘ite neighborhoods.

Al-Maliki’s government insists that the Iraqi security forces can secure the capital, but if waves of bombings persist, the specter of mobilized, vigilante Shi‘ite militias is a troubling possibility.