BAGHDAD, Sept. 9 (UPI) -- The first brigade of U.S. soldiers designated exclusively to advising and assisting Iraqi forces arrived in the south of the country, the Pentagon announced.

Members of the 3rd Armored Cavalry Regiment arrived to replace soldiers in the 3rd Infantry Division's 3rd Brigade as part of Operation New Dawn.

U.S. combat operations came to a formal end Aug. 31, more than seven years after the U.S. military invasion of Iraq. U.S. soldiers operating in Iraq are there as part of the new mission meant to train Iraqi soldiers.

The U.S. Defense Department described the unit as a "combat-capable" brigade that will train forces in the five southern provinces of Iraq.

Their arrival comes after two U.S. soldiers were killed and nine others were wounded Tuesday in Salahuddin province. Their attacker was wearing an Iraqi army uniform, though the U.S. military said it was unclear if he was an Iraqi soldier.

U.S. Army Brig. Gen. Jeffery Buchanan, a spokesman for U.S. forces in Iraq, said the official investigation found that the attack on U.S. soldiers in the central province was deliberate.

"It doesn't affect our strong commitment to the mission of advising and assisting the Iraqi security forces as they continue to sacrifice each day for security and stability in their nation," he added. "We stand firmly beside them."