Operation Swarmer involves more than 50 aircraft and 1,500 Iraqi and US troops as well as 200 tactical vehicles.
The target is suspected insurgents operating near the town of Samarra, 60 miles north of Baghdad.
A statement said the assault was launched on Thursday morning and is expected to last several days.
Samarra was the site of a bombing attack last month on a Shi'ite shrine.
The attack sparked sectarian reprisals and pushed Iraq to the brink of civil war.
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ping
A friend of mine was in Samara for awhile. He is home now. I just called to tell him to watch this on Fox.
While he was there I sent him lots of care packages, plus some to get to the right people for Iraqi children in the area.
Who Hoo, I hope we kick some butt there, and get some big terrorists while at it.