The "war on terrorism" is a significant example of the effectiveness of asymmetrical strategies; the "David and Goliath Effect". Like toreadors, waving a cape at a raging bull in the bull ring, al-Qaeda fields a single operative with explosives in his underwear at the cost of a plane ticket and we spend a billion dollars installing scanning machines in airports all over the country.
Al-Qaeda abandons Afghanistan for the tribal regions of Pakistan leaving us to spend billions of dollars fighting the Taliban who's goals don't extend beyond the national boundaries of Afghanistan. Al-Qaeda's cost is next to nothing but the cost to us is immeasurable.
A large military presence in a foreign country only serves to inflame indigenous resentments. Our presence in Iraq and in Afghanistan is a recruiting tool that al-Qaeda could only imagine in their wildest dreams and, over the better part of the last decade, they've learned how to push the right buttons to keep things going.
They don't need to "win". They only need to keep us chasing our tails to achieve their goal of driving us to bankruptcy. For them to merely survive is the big win for them.
We cannot "win" as long as we continue trying to "fight terrorism" on their terms ... as long as we pursue al-Qaeda as if it were a military entity by putting our military force into the field we are playing to their strengths. Like the art of jujitsu, they are using our sheer weight against us. They count on our macho bravodo that dictates, once committed, we cannot back away. Like a bull in a bull ring, we cannot stop chasing the illusive capes.