Shiite cleric Muqtada al-Sadr speaks during a media conference in Najaf, Iraq, 100 miles south of Baghdad, Saturday as hundreds of his supporters stormed the Green Zone government center in Baghdad.(Photo: Anmar Khalil, AP)

Why you should know who Iraqi cleric Muqtada al-Sadar is

Gregg Zoroya, USA TODAY 5:08 p.m. EDT May 2, 2016

Since the U.S.-led invasion of Iraq in 2003, Muqtada al-Sadr has been an unpredictable force to reckon with as the U.S. military and the Iraqi government have learned.

After leading a protest that stormed the Iraqi parliament, the 42-year-old Shiite cleric stands to dictate widespread changes to Iraq's government.

Al-Sadr was able to "demonstrate that you can't ignore him and he can pierce the corridors of power, literally," said Michael Knights of the Washington Institute for Near East Policy, an expert on the cleric. "His objective would be to increase his own clout as a political kingmaker."

Saturday, hundreds of al-Sadr's followers stormed the heavily fortified Green Zone, the government center of Baghdad, and broke into parliament, sending politicians fleeing. Order was finally restored later that day.

The unrest raised doubts about the political stability of Iraq and occurred at a fragile moment when the government of Prime Minister Haider al-Abadi is struggling to mount an effective counteroffensive against Islamic State forces occupying the nation's second-largest city, Mosul.