<P> Throughout the early years of the war , British foreign secretary Lord Russell , Napoleon III , and , to a lesser extent , British Prime Minister Lord Palmerston , explored the risks and advantages of recognition of the Confederacy or at least offering a mediation . Recognition meant certain war with the US , loss of American grain , loss of exports , loss of investments in American securities , potential invasion of Canada and other North American colonies , higher taxes , and a threat to the British merchant marine with little to gain in return . Many party leaders and the general public wanted no war with such high costs and meager benefits . Recognition was considered following the Second Battle of Manassas , when the British government was preparing to mediate in the conflict , but the Union victory at the Battle of Antietam and Lincoln 's Emancipation Proclamation , combined with internal opposition , caused the government to back away . </P>
which battle ended britain 's support for the south
the Battle of Antietam