After the 2003 invasion of Iraq and the civil war that followed, the Americans dismantled the Iraqi army and intelligence services and purged Saddam-era officials at all levels. As a result, Iraq became weak, decentralized, and fragmented. The federal authorities were unable to restore order even in areas near Baghdad, let alone in more distant provinces.
The situation was further complicated by the hostile relations between Iraq’s various ethno-religious communities: Shiites, Sunnis, Kurds, Yazidis, and Christians. These communities largely assumed the functions of the state, including when it came to issues of security and defense. Every village and every city neighborhood sprouted their own militias, mini-armies tasked with protecting residents from hostile neighbors and criminals.
Some of these groups came under American patronage, most notably Sunni militias collectively known as the “Sons of Iraq.” The main mission of these groups was to counter Al-Qaeda, which was then rightly seen in Washington as the main security threat in the region as a whole.
Iran, meanwhile, sought to expand its influence in Iraq as part of an effort to prevent the neighboring country from becoming a satellite of the United States. For this reason, Iran also invested in Iraqi militias and even made them one of its main tools for manipulating Iraqi politics.
The ayatollahs bought weapons and equipment for the Iraqis, paid militants’ salaries, and trained them — mostly fellow Shiites, of course, but also several Christian, Yazidi, and even Sunni groups.
There were also some curious overlaps. Local authorities sent large numbers of Shiites from pro-Iranian movements into the “Wolf Brigade,” an American-created police special forces unit that included members of the openly anti-American Badr Organization. Most Shiite groups, however, were fully oriented toward Tehran right from the outset.
In effect, these were units of Iran’s armed forces made up of Iraqi citizens. The Iraqi government, led for many years by the pro-Iranian prime minister Nouri al-Maliki, simply turned a blind eye to Tehran’s activities in its rear.