The heavy fighting that erupted in Afghanistan over the weekend is a reminder that a great deal remains to be done in that country, even as we begin to move against al Qaeda in other places. It also indicates a course correction in the U.S. approach that led to problems earlier this year around Tora Bora.

The "Afghan Model," the employment of heavy and accurate air power in conjunction with allied fighters, supported by a small number of U.S. special-operations forces (SOF) to plan and coordinate air strikes, has been touted by some as the wave of the future for the American military. The model seemed to work well earlier in the war as the Taliban collapsed and city after city fell to America’s Afghan allies. It seemed to work again as the al Qaeda base area around Tora Bora was pulverized by massive air strikes.

But even as the campaign in Afghanistan moved from one apparent success to another, dissenters raised some troubling questions. The British press reported that unnamed sources within the Special Air Service (SAS), Britain’s elite SOF, argued that the U.S. approach allowed Osama bin Laden and his ranking al Qaeda lieutenants to escape.

They claimed that the allies had reliable intelligence regarding the location of Osama bin Laden, and that he could have been killed or captured in a raid by the SAS or U.S. SOF, but that the U.S. decision to rely almost exclusively on anti-Taliban Afghans to carry the bulk of the ground combat gave the al Qaeda leadership time to slip away. On the one hand, the anti-Taliban fighters did not place the same priority on capturing or killing the al Qaeda leaders. On the other, press reports indicate that Osama bin Laden and his lieutenants had vast amounts of cash available to bribe local warlords and tribesmen, enabling them to make good their escape when the time came. Critics also took the U.S. to task for not adequately sealing the border between Afghanistan and Pakistan.

Hindsight is always 20/20, but the current round of fighting indicates that the U.S. has modified its approach to the war. It appears that U.S. ground troops are more directly involved in the fighting and that they are taking the lead in sealing off al Qaeda escape routes into Pakistan. The risk associated with this change is already apparent—the likelihood of heavier U.S. casualties.

But we don’t have any choice. Ultimate success in Afghanistan will require ground troops beyond SOF and more direct employment of those ground forces in combat. U.S. air power will continue to be the cornerstone of the war effort, but it is more effective when used in conjunction with ground forces. To use a Zen analogy, air power and ground forces are like the blades of a pair of scissors. Both blades are necessary for cutting.

The intensity of the fighting indicates that the modified approach is working. At Tora Bora, the enemy was able to slip away to fight another day. This time it appears that their escape routes have been cut off. Having been fixed by the ground effort, they now present a lucrative target for massive, concentrated air strikes.

We have entered into is a more dangerous phase of the war and it is entirely possible that there will be more U.S. casualties. Whether it will be the last phase of the war remains to be seen, but it is a necessary one on the road to final success.

Mackubin Thomas Owens is professor of strategy and force planning at the Naval War College in Newport, RI, and an adjunct fellow of the Ashbrook Center. The views expressed here are his own and do not reflect the position of the War College, Navy Department, or Department of Defense.