gregory johnsen author of "the last refuge: yemen, al-qaeda and america's war in arabia," thank you. >> woodruff: next, to the multi- national fight against another terrorist group, the islamic state. representatives from several countries, including the u.s., met in london today to discuss their efforts to cripple the group. our chief foreign affairs correspondent margaret warner is there and filed this report. >> warner: 21 foreign ministers came to the london conference table. in the face of criticism that gains against islamic state forces in iraq have been slow in coming. but secretary of state john kerry brought an upbeat assessment, using the militant group's arabic acronym. >> we are taking out daesh's fighters in the thousands thus far, single digits, but thousands. their commanders, 50% of the top command, has been eliminated. >> warner: president obama began assembling the international coalition last august after islamic state forces surged into iraq, and threatened iraqi kurdistan. the group now encompasses some 60 nations, including several arab and gulf states, working

gregory johnsen is a writer at large and the author of the last refuge.n new york, matthew waxman, a fellow with the council of foreign relations and a professor at columbia. what we know about what happened in libya? >> a group claiming to be the libyan branch of isis carried out this attack at the corinthian hotel. it is really unclear who this group is. but the credibility of the claim seems to be high. they announced it as the attack was beginning. killed a number of people. it raises questions about how t he sway of this group is. it does not matter if it was essentially planned from isis headquarters in syria or if they are affiliates in libya. the point is that this group has -- it's idea has tremendous resonance across the region. you have various jihad e factions aligning themselves voluntarily with isis. >> where else do you see it happening? >> the sinai peninsula. you have a group that claims to act on behalf of crisis in yemen. even from the eastern edge of the islamic world, there are groups pledging allegiance to isis. >> the economist wrot