Giuseppe Garibaldi sympathized with the Union, even offering to fight for Lincoln and Tsar Alexander II outright supported Lincoln's efforts. The Union was less focused on securing aid from foreign powers than it was focused on keeping them out of the war however. They succeeded thanks to Secretary of State William H. Seward and Ambassador to the United Kingdom Charles Francis Adams.

The Confederate states believed that they could eventually convince the United Kingdom and France to come to their aid at least financially via cotton diplomacy, withholding cotton produced in the South to cause the price of cotton to rise drastically. It ultimately failed as the British and French sought cotton in other places, such as Egypt and India, causing great harm to the Confederate economy.

Also worth noting is that Canada was still British and bordered the Union, while the French invaded Mexico in 1862, installed the Austrian Archduke Maximilian as King of Mexico, and bordered the rebellious Confederacy.

Another source of contention between the Union and the United Kingdom were naval incidents such as the Trent Affair (when the Union intercepted a British ship and removed two Confederate diplomats) and the CSS Alabama claims (when British businesses built ships for the Confederates to break through the Union blockade)