The many years of British pressure on the United States to join vigorously in fighting the Atlantic slave trade had been neutralised by the southern states. However with the onset of the American Civil War, the Lincoln administration became eager to sign up, humanitarian and military objectives combined. To the North, anti-slavery was an important military tool with which to harm the Confederate economy. It also won praise, sympathy and support on the international stage, and dampened international support for the Southern States who vehemently defended their right to keep slaves. In the Lyons–Seward Treaty of 1862, the United States gave the UK full authority to crack down on the Atlantic slave trade when carried on by US ships.Conway W. Henderson, "The Anglo-American Treaty of 1862 in Civil War Diplomacy." Civil War History 15.4 (1969): 308–319. online With the end of hostilities the UK and the US would continue cooperating, and in 1867, Cuba, under much pressure from the two nations, gave up its trade.
