I think Richard Lyon described it best down below - winning against guerillas is the business of empire.

It has been done in the past, so it could certainly be done again. But the requirement for success seems to be massive brutality that would make any modern regime, even Bush's, look angelic.

And yes, you need a standing army, and local volunteers/conscripts.

The idea that war is a series of pitched battles has only really been true in exceptional situations. The battles are the visible part of a more organic process which relies on diplomacy, economics, politics, and espionage - anything to gain an advantage.

Stopping an insurgency doesn't just require regime change, it requires culture change. You can only really do it by decapitation (sometimes literal) of the insurgency's leadership, followed up by repression of the followers.

Politically today this is unacceptable. So it's very likely impossible for any nominally accountable democracy to beat an insurgency by violence alone.

But is it a war? It's not in the traditional sense - not just because there are no pitched battles, but because wars traditionally end either when armies are destroyed or leaders are killed.

When you don't have an army to fight, and you don't have a single leader in command to take out, it's hard to know whether you've won or not.