By Missy Ryan BAGHDAD, Nov 16 (Reuters) - About 600 U.S. troops launched a pre-dawn assault south of Baghdad on Friday against al Qaeda fighters linked to the kidnapping of two soldiers six months ago, the U.S. military said. F-16 warplanes dropped two 500-lb bombs on potential escape routes while helicopters flew the U.S. troops, along with about 150 Iraqi soldiers, into the Sunni Arab villages of al-Owesap and al-Betra west of the Euphrates River. Two U.S. soldiers have been missing since their patrol was ambushed on May 12 near Mahmudiya, about 30 km (20 miles) south of Baghdad in a Sunni Arab insurgency stronghold known as "the triangle of death". Four other U.S. soldiers and an Iraqi interpreter were killed in the attack, responsibility for which was claimed by al Qaeda-led Islamic State in Iraq. A third U.S. soldier was abducted but his body was found in the Euphrates almost two weeks later. "The group of al Qaeda that we believe to be operating in that area, we suspect they had involvement in the May 12th attack," said U.S. military spokeswoman Major Alayne Conway. There was no immediate information about whether any militants had been killed or detained in the early stages of Operation Marne Courageous, which began at around 4 a.m. (0100 GMT) on Friday, she said. SURGE While violence has been falling in Baghdad and other areas in the past two months, Conway said U.S. forces want to establish a bigger presence in an area south of the capital still known as a stronghold for Sunni Arab militant groups. U.S. forces were "trying to exploit any intelligence, any type of avenue to explore where those soldiers are", Conway said. "We continue to search for these guys." U.S. military and Iraqi civilian casualties have dropped sharply in the past two months, the falls attributed to the "surge" of 30,000 extra U.S. troops this year and the growing use of neighbourhood police units organised by tribal sheikhs. Another factor has been moving U.S. troops out of large bases into combat outposts where they live among local Iraqis. Conway said such a patrol base would be established as part of the new operation. "You go in, you establish a foothold, you hold the area," she said. Once the U.S. outpost was in place, reconstruction and governance projects in the area would follow, Conway said. (Editing by Paul Tait and Ralph Boulton)
