<P> The United Kingdom (the United Kingdom of Great Britain and Ireland) remained officially neutral throughout the American Civil War (1861--1865). It legally recognised the belligerent status of the Confederate States of America (CSA) but never recognised it as a nation and neither signed a treaty with it nor exchanged ambassadors . Over 90 percent of Confederate trade with Britain ended, causing a severe shortage of cotton by 1862 . Britain financed blockade runners that sent munitions and luxuries to Confederate ports in return for cotton and tobacco . Top British officials debated offering to mediate in the first 18 months, which the CSA wanted but the U.S. strongly rejected . </P> <P> The British elite tended to support the Confederacy, but ordinary people tended to support the United States . Large - scale trade continued between Britain and the U.S.: The U.S. shipped grain to Britain and Britain sent manufactured items and munitions . Immigration continued into the US, with many Britons volunteering for its army . British trade with the Confederacy fell over 90% from the prewar period, with a small amount of cotton going to Britain and some munitions and luxury goods slipped in by numerous small blockade runners . They were operated and funded by British private interests . They were legal under international law, and caused no dispute between the US and the UK . </P>

What caused tension between the union and great britain