The role of the American military in Alaska has been important since World War II. The only successful invasion of American territory since the War of 1812 was in the Aleutians during WWII.. Alaska also played a very significant strategic role during the early stages of the Cold War, when the chief defense of the free world rested on strategic air forces carrying nuclear weapons. Many of the military facilities in Alaska today date from the Cold Wars, though their mission is much changed. Alaska has always welcomed the military, perhaps because residents feel rather isolated from the rest of the country.

http://sled.alaska.edu/akfaq/akmilit.html

Today the military has three principal missions in Alaska. Army, air and naval forces can be deployed to protect the security of the Alaska Pipeline. This protection was demonstrated in the traumatic hours following the terrorist attack on the World Trade Center towers in September, 2001. Alaska has also several facilities, primarily the launch center at Kodiak and the radar site at Ft. Greeley , that are part of the missile defense shield of the United States. And the 172nd Infantry Brigade, stationed at Ft. Wainwright, is part of the Army's rapid deployment capability to move needed troops quickly to any part of the globe where American forces may be needed. The U.S. Coast Guard has a special role in Alaska as well, given that the state has more than 20,000 miles of coastline. The Coast Guard mission includes law enforcement - preventing smuggling, fisheries poaching and drug traffic -, and search and rescue, for ocean-going vessels, fishing boats operating in Alaska and recreational boaters.