What event nearly prompted British intervention in the American Civil War?

The Trent Affair is a significant event that nearly led to British intervention in the American Civil War due to its diplomatic implications. This incident occurred in late 1861 when a Union naval officer captured two Confederate diplomats, James Mason and John Slidell, aboard the British mail ship RMS Trent. The British government viewed this act as a violation of neutral rights since the ship was a British vessel.

The reaction from Britain was one of outrage, as they demanded the release of the diplomats and an apology from the United States. The situation escalated to the point where Britain prepared for potential military action against the Union. However, President Abraham Lincoln and his administration recognized the precariousness of the situation and ultimately decided to release Mason and Slidell to diffuse tensions.

This episode highlighted the fragile nature of international relations during the Civil War and underscored the potential for foreign involvement. It also illustrated how the Union sought to maintain diplomatic relations with Britain while striving to prevent any recognition of the Confederacy that could turn the tide in the war.