The videotape of al-Qaeda deputy Ayman al-Zawahiri broadcast on Thursday is the latest in a series of recent messages sent by the terrorism network's top leaders that analysts believe may be part of a campaign to reassert themselves, even as they remain isolated by US and Pakistani forces.

Since April 2004 there have been at least nine tapes from al-Qaeda’s two leaders – Mr al-Zawahiri and Osama bin Laden – all of which have drawn close scrutiny from security agencies and terrorism analysts, since Mr bin Laden has repeatedly said his public statements were important sources for those wishing to understand the network's ideology and political goals.