The movement of immense amounts of military supplies, vehicles and equipment from Afghanistan will be time consuming and costly for the International Security Assistance Forces (ISAF). Pakistan has been a pain in the rear - at times closing its land routes to the Pakistan seaports for as long a six months at a time. In addition, corruption, labor strikes, high costs, theft, and clogged seaports have hindered the movement of equipment and supplies over the years through Pakistan. Moving vast amounts of heavy equipment by air is costly (and we don't have enough air transport). One way out is through the land routes by truck and rail in central Asia across the 'stans along the Old Silk Road (or is it the New Silk Road?) into Europe and ultimately to seaports along the Baltic, Mediterranean, or Atlantic waters. However, movement through the 'stans has its own host of problems.
Uzbekistan has offered to help solve this difficult problem - with some give and take (or mostly taking on their part). They wouldn't terribly mind if along the way out we dropped off some military equipment such as armored vehicles, helicopters, etc. for Uzbekistan to keep. Read more in "As NATO Prepares for Afghan Withdrawal, Uzbekistan Seeks War's Leftovers", The New York Times, January 31, 2013.