Decreasing seasonal sea ice in the Arctic has made some Arctic waters navigable for longer periods and, as a result, may contribute to new economic opportunities in commercial shipping, oil exploration, and tourism. This could eventually increase the need for a U.S. military and homeland security presence in the Arctic, particularly in the maritime environment. This book discusses the role of DOD in the Arctic based on recent strategic guidance and its assessment of the security environment in the region; the actions taken by DOD to address near-term capability needs; and the efforts DOD has under way to update plans for the Arctic and identify future capability needs.