other muslims, seen as heretics, tactics that today sound hauntingly familiar. >> with a $25 million price on his head, there is no one the u.s. wants to capture or kill more than zarqawi. >> the cia had been tracking his every move. in june of 2006 u.s. forces killed him with two 500-pound bombs. >> tonight the most wanted terrorist in iraq is killed in a massive united states air strike. >> zarqawi. >> zarqawi, he said, was eliminated. >> zarqawi's death is a severe blow to al qaeda. >> but as it turned out, the movement zarqawi began would survive that blow. when we come back, the rise of the leader of isis. >> he wasn't considered from everything that we know now, a high-level detainee. >> inside an american prison.