Waging expeditionary warfare in a landlocked country is expensive, requiring long and vulnerable supply lines. In Afghanistan, such vulnerabilities have been marginal in a military sense, because the enemy had a limited capacity to disrupt supply flows. In a political sense, however, vulnerability has been high. For more than a decade, the United States and its International Security Assistance Force allies have had to weave through considerable political obstacles to keep their soldiers in Afghanistan supplied. The Creation of the Northern Distribution Network Logistics personnel look for supply routes that are the most timely, cost efficient and secure. After the initial invasion of Afghanistan, these lines primarily involved transit by truck across two main routes through Pakistan from the port of Karachi. This gave Pakistan enormous leverage over parts of U.S. policy regarding the war.