The 10-year war

>> tense night in the white house , later they were able to hear from inside the white house the kind of spontaneous uproar across the street as people flowed into the streets of washington, d.c. and the park across the street from the white house to celebrate the news. all of this brings us back to richard engle, who is in libya. and richard , you and i have on occasion been given a good glimpse inside u.s. military special operations . but no one can match your time embedded with the u.s. military or speak with the authority you have on this ten-year effort to find this one man.

>> reporter: it is incredible when you look back at it. ten years, america's war on tear rmp and how costly it has been. a trillion dollars, thousands of american families, american soldiers who have lost their loved onesp this fight. and it has just been a war that has set the tone for american society for the last decade. after 9/11, the united states mobilized for war. seeking justice and revenge. troops invaded afghanistan almost immediately. within two months, al qaeda 's hosts, the taliban, were thrown out of power. osama bin laden got away. but regime change in afghanistan , done with few troops and high technology , seemed so easy. the bush white house tried it again in iraq . u.s. officials said saddam hussein was developing weapons of mass destruction and linked iraq to 9/11 and bin laden .

>> the reason i keep insisting there was a relationship between iraq and saddam and al qaeda was because there was a relationship between iraq and saddam and al qaeda .

>> reporter: afghanistan and iraq were lumped together in what was called a global war on terrorism . the truth was, there was never a connection between iraq and osama bin laden . there were no weapons of mass destruction , either. but when civil war in iraq broke out, american troops were stuck. deployment after deployment trying to stop the daily carn carnage. the cost was enormous. more than 4,400 american troops dead. along with 150,000 iraqis. and it was a distraction from the united states ' original mission to find bin laden , stop al qaeda , and prevent another 9/11. with american troops tied down in baghdad, al qaeda and the taliban slipped back into afghanistan . a fight the united states is still waging. but now, a major victory the united states has had to wait ten years to see. osama bin laden is dead. killed not by a massive troop deployment but by a commando raid carried out by a few dozen highly trained men and helicopter said. with osama bin laden 's death, this chapter of america's war on terrorism , a war that has defined the military, defined american culture , even, may be ending.

>> richard engle always on the road covering conflict for us. tonight in libya, richard , thanks.