During the American Civil War, the North held major economic, manufacturing, and manpower advantages over the South. For the Confederacy to win the war, they would likely have to depend on foreign help. Officials in the Confederacy hoped that European powers such as Great Britain and France, both of which traded extensively for Southern cotton and textiles, would recognize the Confederacy as an independent nation, or, would declare war on the United States.
At the onset of the war, Great Britain issued a proclamation of neutrality, though they considered the division of the United States to be an inevitable conclusion. Because they considered the Confederacy to be in a state of belligerency, the British Crown authorized all Confederate and British interactions in Great Britain with the exception of trade for weapons and ammunition. On November 8, 1861, U.S. Naval forces under the command of Charles Wilkes captured a British mail vessel returning to Great Britain in the Caribbean Sea. Wilkes captured and detained two Confederate agents, James Mason and John Slidell, who were travelling to England in an attempt to persuade the British Crown to recognize the Confederacy as a sovereign nation. When the news hit the Northern presses on November 16th, support for the seizure was nearly universal, though its legality soon came into question in the North.
In Great Britain, Parliament (British government) was outraged. Most viewed the seizure of a British vessel in international waters as an insult to their national honor and a violation of maritime (sea) laws. In their official response to the seizure, British officials demanded the immediate release of the prisoners as well as an apology and declared it an act of war. British financial markets declined rapidly as the threat of war between England and the United States intensified. Furthermore, British military officials sent over 17,000 soldiers to Canada to prepare for combat and to possibly invade the state to Maine, which the British believed, may have been agreeable to being annexed by Canada.
Despite the intensification of hostilities, President Abraham Lincoln and his advisors eventually relented and claimed Wilkes acted without orders. The two British agents, Mason and Sildell, were released and allowed to complete their trip to Great Britain and arrived on January 8, 1862. The two agents were unable to convince British officials to recognize the Confederacy as a sovereign nation. Lincoln never issued a formal apology, but his diplomacy averted a war with Great Britain, enabling the United States military to concentrate their efforts in subduing the South.