U.S. strategic shift in Afghanistan

(CNN) - As U.S. Marines continue their drive to push the Taliban out of its stronghold in southern Afghanistan, a new military strategy is taking root.

When you take a town from the enemy, hold it. When you push the enemy into the hills, keep him there.

Make the local population feel more secure, and then cut the Taliban's financial lifeline by convincing Afghan farmers to grow an increasingly lucrative wheat crop instead of poppies.

It's a strategy many U.S. military leaders wanted to pursue for years. Until recently, however, they didn't have sufficient troop levels to pull it off.

"They're not just doing an offensive push to get bad guys. They're going in to hold the area and stay there," a senior defense official recently told CNN.

"This approach is indicative of (commanding Gen. Stanley) McChrystal's philosophy: measuring success by the number of Afghans protected, not bad guys killed."