The Khyber Pass (pictured), which along with the similar Chaman Crossing, carries 75% of all US supplies transported into Afghanistan. That amounts to approximately 300 tanker and container trucks combined navigating these serpentine routes on any given day.
Trouble looms on the horizon as the United States and NATO increase troop commitments in the landlocked nation of Afghanistan. As personnel numbers go up so to does the need for food, oil, construction materials, weaponry, ammunition, medical supplies and more. Unfortunately, these equipment requirements are running up against a supply network which is operating near capacity and is dangerously exposed to potentially devistating disruptions. Compounding this issue is the recent decision (flipflop though?) by Kyrgyzstan to close the Manas Air Base, an important routing point. If the US and allies are to follow through on their plans for Afghanistan, new and more reliable routes must be found.
Afghanistan is a country difficult to supply by virtue of it being landlocked, surrounded by mountainous terrain and with limited transportation infrastructure (one paved round which rings the country). Compounding this problem is neighbors resistive to Western operations. To the west is recalcitrant Iran, to the north is the resurging Russian Sphere of influence, to the south is a lack of roads crossing from Pakistan into Afghanistan, and to the east are Pakistan's Federally Administered Tribal Areas where Taliban forces operate.
Supplying troops now is mainly accomplished via road, with trucks driving from Pakistan's port city of Karachi and heading north and then entering Afghanistan by one of two ways (see map above, roads in yellow). The southern way is the Chaman Crossing and northern one is the Khyber Pass (pictured at top). The Khyber Pass is the preferred delivery route because it affords safer (though hardly safe!) transit to Kabul and northern Afghanistan where most troops are based. (The southern route after passing through the border town of Chaman then heads north across the Kandahar province, a stronghold of Taliban activity, before finally arriving in Kabul.) With these two routes carrying 75% of coalition supplies, you can imagine the unease logistics causes Pentagon planners.
Alternative transit routes are limited and present significant geopolitical opportunity costs to cultivate, though with the importance of operations in Afghanistan, high prices must be paid. Before exploring routes from the north I will briefly address the route Iranian route from the west.
The United States is facing the potential crisis of nuclear armed Iran. To deter this challenge, the US is pursuing a multi-pronged approach leveraging diplomacy, military determent, and economic incentives. With the coercive toolkit significantly engaged and little results seen, now is hardly the time to ask for favors from Iran when Tehran is likely to demand quid pro quo. That is not to say we shouldn't keep our options open, only that we can expect Iran to demand a price we are unwilling to pay.
To the north of Afghanistan are the former Soviet Republics of Turkmenistan, Uzbekistan and Tajikistan, where Russian influence stands tall in the face of American' interests. In recent weeks and months we have seen Russian meddling in the region, with the most obvious case being closure of the Manas Air Base to the US military. While taking this antagonistic posture Russia has also offered a more conciliatory tone with permission for non-military transport to pass through its territory. Additionally, we can assume that Russia had a hand in the recent offers by Turkmenistan and Uzbekistan to also allow transport of US and NATO supplies through their airspace and on their railroads and roads.
Following these mid-February offers, the United States began shipping train-loads of cargo from the Latvian port of Riga across Russia, Kazakhstan, Uzbekistan and to the Afghanistan border (I don't know the railroad mileage though a straight line measures 2400 miles).
Most recently, Kyrgyzstan has begun to show mixed signals on whether it intends to follow through with the base closure plans. This development is exciting for two reasons. First, it appears that the Kyrgyzstan termination of the US lease on Manas Air Base was foremost a calculated financial manoeuvre. By extension, we can secondly assume that the Russian meddling in the "Swiss Stan" of Central Asia was less than I have argued. Both pieces of news are good news; a window of opportunity is open in regards to the base and Russia has meddled less than first appeared. The backing down of Bishkek (literally Kyrgyzstan's capital) is likely a result of the US finding alternative routes (thereby reducing the value of Manas), questionable financial promises by Russia (no payments have been made), and Kyrgyzstan feeling acutely exposed to the downturn (industrial outputs are down 25%).
Although the logistics of supplying coalition forces in Afghanistan are improving, there still exist two important problems. With the future of Manas still in limbo, the US must search out alternative air base(s) as railways cannot replace the function of Manas; specifically, that is transit hub for 90% of all troops passing into Afghanistan and valuable staging area for KC-135 refueling tankers. A potential alternative is the Karshi Khanabad air base in Uzbekistan which the US used until 2005 (until being forced out over human rights protests).The second challenge is delivering weaponry into Afghanistan. Optimally, an additional supply route (to the exposed Pakistani/Afghani road network) would be found. Unfortunately, alternatives are limited to flying all military supplies in or convincing a combination of Central Asian nations to allow non-humanitarian supples to pass through. This challenge may pose the hardest of the two.