combat troops out of afghanistan by the end of 2014, the fight against al qaeda is increasingly turning to yemen. as nbc s chief foreign correspondent richard engel reports, the escalation of violence under scores the new threat. reporter: the suicide bomber was disguised as a soldier. he tucked into a crowd at a rehearsal for a military operate in sanai, detonated a bomb and killed nearly a hundred people. yemen s defense minister narrowly escaped with his life and officials say it s likely the work of al qaeda in yemen. while the u.s. has decimated al qaeda elsewhere, the militant group has grown in yemen because the country hasn t had an effective government for a year. but the arab spring finally toppled yemen s former president and the new president is trying to re-establish order and crack down on al qaeda. u.s. military officials tell nbc