The architects of America's global war on terror acknowledge that the conflict cannot be won by bombs and bullets alone.They say it is also a defining war of ideas in which a key weapon against Islamist extremism is 'public diplomacy' and the power of persuasion.On the anniversary of 9/11, Stephen Sackur talks to James Glassman, the State Department's new chief of public diplomacy.Is America now equipped to win a worldwide propaganda war?