Troops from the US military's 172nd Stryker Brigade began arriving in Baghdad on Saturday to help curb the sectarian bloodshed that has left thousands dead in the Iraqi capital.
The brigade is being brought from the northern city of Mosul to Baghdad to beef up an ongoing security plan, Operation Forward Together, which has put 50,000 Iraqi and US soldiers on the streets of the city.
The 172nd's distinctive "Stryker" vehicles, a wheeled and armoured troop carrier, could be seen on the streets in the mainly-Sunni west of the city.
"Around 3,700 troops from the brigade are being repositioned from up north to support the ongoing Operation Forward Together," said US military spokesman Lieutenant Colonel Barry Johnson.