DoD makes use of five different distribution channels to sustain U.S. military forces overseas. Three are air delivery channels and two are by sea. These channels offer varying speeds of delivery and have different costs. In addition to these variables, there are certain practical constraints that must be taken into account in making choices among channels, and for surface transportation, the marginal cost of additional inventory must also be considered. In this briefing, we analyze the implications of all these factors for how the channels should be used--which transportation modes should be chosen and where materiel should be stocked--to provide effective support as efficiently as possible. We describe the distribution choices for some illustrative units in Iraq and compare them with the ideal model resulting from our analysis. We find that, through gradual evolution, the sustainment structure for Iraq is beginning to match the model. We offer several guidelines for improving sustainment in the near term by bringing current practices closer to the ideal.