Shortly after U.S. troops left Iraq - and with Iraqis worried that their forces will be unable to keep the country secure - a string of terrifying bombings killed nearly 70 people and shook the nation.
The likely culprits: an al-Qaida offshoot bent on pushing the country into civil war.
Analysts say the Islamic State of Iraq, which claimed orchestration of the attacks, appears to have set a goal of spreading sectarian strife.
"These acts have been essentially acts to provoke another round of sectarian fighting between Sunni and Shi'ite," said Anthony Cordesman, a Middle East terrorism expert at the Center for Strategic and International Studies in Washington.
"They have been directed at trying to create a situation where Iraq's unity, in terms of its government and its security forces, would be divided to capitalize on the fears and the anger of many Sunnis that a Shi'ite-dominated government is seen as unfair," he said.
The December 22 blasts in Baghdad were not the group's first high-profile attacks. It has been tied to a string of suicide bombings on Baghdad hotels in January 2010 that killed 36 people. The group also says it carried out triple bombings near foreign embassies in Baghdad in April 2010, leaving 41 people dead.
But analysts say the Islamic State of Iraq has reinvented itself over the years, including changing its name.
The group was founded in 2003 by Abu Musab al-Zarqawi, a Jordanian militant and alleged mastermind of terror who was killed in a 2006 American air strike. Shortly after establishing the group, Zarqawi declared allegiance to Osama bin Laden and al-Qaida.
Over the years, the Iraq-based group has gone by names that include the Mujahideen Shura Council, al-Qaida in Mesopotamia and al-Qaida in Iraq.
Analysts say the group began calling itself the Islamic State of Iraq in 2006, in a bid to establish a national movement and set up a shadow government.
Intelligence senior analyst Adam Raisman said the militant group tries to portray itself as an Iraqi force. But it is a "wholly Sunni" group, he said, that draws members from throughout the Arab world.
"The group is comprised of foreign fighters from a variety of countries, as well as Iraqis. From their communications, we have seen that they have fighters from North Africa, Saudi Arabia, from Yemen, from the Arab world," said Raisman, who monitors intelligence for the Washington group, SITE.
Analysts fear Iraqi security forces are ill-equipped to prevent insurgent attacks.
Cordesman said Iraq has about 600,000 people in its security forces, but most are in "ineffective" police units or guard brigades.
"You have an army that lacks the cohesion, the effective command structure, the intelligence capabilities, and among other things, mix of intelligence assets and air mobility necessary to react as quickly and effectively as it should," he said.
"You also have a police that has been steadily deteriorating in quality, becoming more and more political and more and more local," he added.
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