A dozen explosions echoed across the marine base as artillery gunners fired 155 mm Howitzers cannons to ensure the accuracy of their targeting, said Major T.V. Johnson.

"They are realigning the guns as the troops shift positions," said Johnson, a spokesman for the 1st Marine Expeditionary Unit.

He said the exercise would ensure the troops on the ground can rapidly call for back-up fire if they come under attack from "the bad guys."

Since Friday, the marines who have besieged Fallujah for almost a month, have been gradually moving back from positions around the city to allow a new Iraqi force, the Fallujah Brigade, to take over security duties.

WAR.WIRE