 The war, however, accentuated a tendency already existing and dealt a blow from which the merchant marine failed to recover until artificially revived during World War I.In 1861 registered American tonnage in foreign trade amounted to 2,496,894 tons and in 1865 to 1,518,350, while the percent of imports and exports carried in American ships dropped in the same years from 66.2 to 27.7.The decrease of tonnage in these years of some 900,000 tons was chiefly due to two causes.