United States Merchant Marine (The Era of Relative Peace)

The United States Merchant Marine refers to either United States civilian mariners, or to U.S. civilian and federally owned merchant vessels. Both the civilian mariners and the merchant vessels are managed by a combination of the government and private sectors, and engage in commerce or transportation of goods and services in and out of the navigable waters of the United States. The Merchant Marine primarily transports cargo and passengers during peacetime; in times of war, the Merchant Marine can be an auxiliary to the United States Navy, and can be called upon to deliver military personnel and materiel for the military.

History
See also: 

World War III
The outbreak of the war in Europe saw the REFORGER convoys transiting the Atlantic. U.S. Navy ships, which included destroyers, cruisers, frigates, troop carriers, and replenishment ships were sent out from naval stations in Key West, FL; Norfolk, VA; and Philadelphia, PA. President George H.W. Bush federalized both the Merchant Fleet and the Civil Reserve Air Fleet were federalized to operate under the Department of Defense. The Merchant Fleet was responsible for delivering troops, vehicles, equipment, and supplies from the U.S. to the United Kingdom, which was the main allied base as it was not invaded by the Soviet Union. The Merchant Fleet also made stops in Canada and Greenland on their way to Europe. Traveling mainly with U.S. Navy escort, the merchant fleet mainly faced danger from Soviet submarines lurking in the Atlantic.

Once the war expanded in the Pacific, the Merchant fleet along with the U.S. Pacific Fleet was deployed to Japan, South Korea, Guam, the Northern Mariana Islands and the Philippines, fulfilling their role like their Atlantic counterparts.

Post-war, the Merchant Fleet continued ferrying supplies and soldiers to rebuilding of the war-torn areas. It was estimated that around 10,000 mariners lost their lives in the war, along with 100-200 civilian ships that were either sunk by WarPac/COM forces or other peacetime incidents.