u.s. and british forces have withdrawn troops from yemen. >> the country is feeling concerns that terror groups will be able to move in and freely mount attacks. here's barbara starr with details. >> reporter: yemen, now on the brink of civil war. amid the rising unrest the oounsz warning the worst may be to come as groups vie for power. >> unless a solution can be found in the coming days the country will fly into further violent conflict. >> reporter: a u.s. official tells cnn, al qaeda fighters, which have vowed to attack the u.s. are now moving quickly to increase recruiting and continue plotting attacks. but the u.s. just became essentially blind on the ground. more than 100 u.s. military band commandos like these who'd been tracking al qaeda known as aqap secretly ordered out of the