Taliban attacks are jumping in the southern Afghan areas that were the focus of the 2010 U.S. troop surge, posing a renewed challenge to the American-led coalition that hoped to pacify the crucial region before withdrawing from the country.

Making sure the fledgling Afghan security forces will be able to hold the Taliban at bay in Kandahar and elsewhere after most American forces pull out over the next two years is the focus of a North Atlantic Treaty Organization (NATO) summit that begins in Chicago on Sunday.

The summit unfolds as the coalition, after saying it has reversed the Taliban's momentum, is gradually transferring security responsibilities across the country to the Afghan troops.

Over the past two years, the farming districts of Zhari, Panjway and Maiwand northwest of Kandahar city -- the cradle of the Taliban movement -- were the key battlefield of the U.S.-led military campaign in southern Afghanistan. The U.S. has held up its successes in routing the Taliban there as proof that it is winning the war.

Pushed out of these rural districts by the surge, the Taliban last year concentrated on Kandahar city, ramping up their campaign of assassinating government officials. This fighting season, however, they appear to have trickled back to their old home turf.

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