U.S. forces have completed their withdrawal from the Korengal Valley of northeastern Afghanistan, The Wall Street Journal reported April 14. After five years of combating Taliban militants, the last U.S. soldiers were airlifted from valley, which is in the Pech district of Kunar province. Top U.S. commander in Afghanistan Gen. Stanley McChrystal explained the move as stemming from a realization that U.S. forces had become "an irritant to the people" in the valley, as opposed to providing the area with security. The pullback from Korengal actually reflects a larger shift in priorities. Washington is adding forces into Afghanistan in a bid to undermine the Taliban insurgency, which has intensified in the past four years. Because the overall U.S. effort in Afghanistan is being carried out with a limited number of troops given the extent of the challenge, McChrystal must be judicious about where he commits forces. Population is key to such decisions. The U.S. strategy entails focusing on 80 key districts. Many of these are among Afghanistan's most heavily populated provinces, and roughly correspond with the country's ring road. Focusing on densely populated areas allows International Security Assistance Force (ISAF) troops to deploy in roughly a third of the country's territory while attempting to impact two-thirds of its population. This allows Western forces to deny the Taliban free rein in important population centers while trying to make progress in the so-called hearts and minds campaign. (click here to enlarge image) Kunar province is adjacent to Bajaur agency, the northern tip of the Pakistan's Federally Administered Tribal Areas. As such, it is a major thoroughfare for both Afghan and transnational jihadists. In March, Pakistani forces acting in coordination with a local tribal militia managed to clear large portions of Bajaur. In the process, they seized control of a 156-cave complex that had housed Pakistani Taliban and al Qaeda-linked foreign fighters active on both sides of the border. U.S. Maj. Gen. Curtis Scaparrotti, the ISAF commander in eastern Afghanistan, acknowledged in an interview with AFP published April 14 that Pakistani action in the tribal belt has led to a decrease in cross-border activity. The Pakistani successes in the northern rim of the tribal belt are still preliminary, however. Given the difficulty of fighting in Kunar's rugged terrain and the lack of support from locals, McChrystal appears to have decided the Western investment in the Korengal Valley was not worth the return — though at this point, U.S. forces have only pulled out of a small area within Kunar. The exit from Korengal probably reflects increasing cooperation between Washington and Islamabad, as it suggests some degree of ISAF confidence in Pakistani gains in the tribal areas just across the Afghan border.