nuclear. >> reporter: only nine countries have nuclear weapons. the theory is they are preventive, hopefully never to be needed in battle. according to the arms control association, russia has the largest number of warheads. just over 6,000. while the u.s. isn't far behind no, other country, not even israel or north korea, has anywhere near this time of capability. most of russia's warheads are not on missile bases. just over 1,400 of them are deployable at the moment. these find. they on weapons like ballistic missiles, submarine missiles and also on bombers. but would russia's president really use them? the defense secretary told the bbc, he thinks putin is bluffing. >> he reminded everyone he has nuclear weapons which starts to set off people being worried. but secondly, he distracted from what's going on in ukraine.