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In the wake of the 2008 terrorist attack on Mumbai, many observers predicted that the outrage would prove a turning point in the global struggle against terrorism. A year on, however, it is far from clear if the attacks, and the lessons they hold out, have in fact changed the world’s perception of the problem of terrorism — and the responses it necessitates.

Few things today are, superficially at least, as consensual as the need to fight terrorism. International public opinion was indeed shocked by the Mumbai attacks; commentators articulated their outrage; leaders expressed their condemnation. If there was any such thing as a global impact of the Mumbai attacks, its nature was at the very least ambiguous.

True, messages of sympathy did abound. At the practical level,...