With Iraq wracked by the worst violence in three years, Prime Minister Nuri Kamal al-Maliki was in Washington this week looking for military aid and other help. This was quite a turnabout, since he had essentially forced American troops to leave in 2011. Since then, the pressures in Iraq have grown, and Mr. Maliki bears much responsibility for the current turmoil.

His plea for assistance is urgent because Al Qaeda in Iraq, a Sunni group and Al Qaeda affiliate that was significantly degraded in 2008, is again a major threat, stoking war against Iraq’s majority Shiites. Since January, more than 7,000 people have been killed in bombings and shootings in outdoor markets, cafes, bus stations, mosques and pilgrimages in Shiite areas.

Al Qaeda in Iraq waged a virulent insurgency that brought the country near civil war in 2006 and 2007, then suffered big defeats from Iraqi Sunni tribal groups and American forces. Since the Americans withdrew, the group has gained strength against Iraqi forces that are incapable of fully protecting civilians and has taken in fighters spilling in from neighboring Syria. These are serious problems. Mr. Maliki, however, has been playing a central role in the disorder. There is no doubt that militant threats would be less pronounced now if he had united the country around shared goals rather than stoked sectarian conflict.

Instead, he has wielded his power to favor his Shiite majority brethren at the expense of the minority Sunnis. The Sunnis, banished from power after Saddam Hussein’s ouster, have grown more bitter as they have been excluded from political and economic life. Mr. Maliki is also at odds with the Kurds, the country’s other major ethnic group in what was supposed to be a power-sharing government.