Following the devastating attacks on its soil, the US made a declaration of war - the 'war against terror'. But so far, the attacks on New York and Washington have not been followed up by any terrorist group.
The US-led operation has not been conspicuously successful outside Afghanistan. Osama Bin Laden has not been found, and the world is nervously anticipating another big attack.
The political fall-out from 11 September helped a whole raft of countries
which had problems with disaffected population groups, but as the BBC's World Affairs editor John Simpson outlines, none of the world's more complicated problems are any easier to solve.
The BBC's Word Affairs editor John Simpson explains the global political shifts and assesses whether the world really has changed.
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