So why do targeted assassinations damage al-Qaeda but have little effect on the likes of Hamas and Hizbollah? The answer lies in the differing nature of these groups. Rather than being a movement firmly grounded in a society, al-Qaeda was a network, built around individuals with charisma and expertise.

Once those kingpins were toppled by missiles falling from a clear sky, the network around them crumbled. Whatever technical or other expertise the targets had built up over the years proved extremely difficult to replace.

Hamas, by contrast, is not the brainchild of one man, but a product of the conflict between Israel and the Palestinians. It has been shaped by the deeper currents within Palestinian society, particularly the growing appeal of radical Sunni Islam. So individuals are not vital to Hamas; those who are killed can be replaced.

If an operative with particular expertise, such as a master bomb-maker or rocket designer, happens to be eliminated, then Hamas may become temporarily less dangerous. The reprieve will last only until a replacement can learn those skills.