“One War at a Time”: President Abraham Lincoln and the Trent Affair of 1861

When faced with a problem, the first step should be to avoid making it worse. President Abraham Lincoln followed this advice when Thirtyaffair, a diplomatic crisis between the United States and Great Britain that began 165 years ago today and nearly led to a third Anglo-American War.

When the American Civil War broke out, Britain, France, and other European countries quickly declared their neutrality. They granted the Confederation the status of “belligerent power”, but did not achieve full diplomatic recognition. The move angered Confederate leaders, who hoped their monopoly on cotton production would bring European countries to their side. The Union, in turn, bristled at the decision to grant the South belligerent status; it gave Confederate ships the legal right under international maritime law to call at neutral ports, purchase weapons, and attack Union ships. U.S. officials have repeatedly warned Europe that its civil war is strictly an internal affair.

The July 1861 Confederate victory at the Battle of Bull Run, the first major battle of the Civil War, convinced Confederate President Jefferson Davis that Europe might be willing to extend full diplomatic recognition to the South. He sent James Murray Mason and John Slidell to Britain and France to argue for recognition. In October, Mason and Slidell escaped the Union naval blockade of Charleston, South Carolina, and sailed to Havana, Cuba. There they were transferred to the British mail ship, the RMS. Thirty hoping to benefit from safe passage to London under a neutral flag.

Mason and Slidell could have arrived in London as they planned without Captain Charles Wilkes. He was a United States naval officer who combined considerable skill and eccentric behavior. Historian George C. Herring described it this way:

An accomplished scientist and naval officer, Wilkes had led the Great American Exploring Expedition on its voyage around the world in the 1840s. Arrogant, bossy, as paranoid as the legendary Captain William Bligh, he was also impulsive and ambitious: he once promoted himself to captain while at sea and ostentatiously donned the uniform he had packed for the occasion.

Wilkes takes command of the USS San Jacinto in August 1861. The ship was patrolling the coast of West Africa as part of efforts to suppress the transatlantic slave trade. But the San JacintoHe soon returned to North America and began pursuing a Confederate ship that was attacking Union merchant ships in the Caribbean.

While in port in Cuba to replenish the San Jacintocoal, Wilkes learned that Mason and Slidell were traveling on the Thirty . Acting without authorization from Washington, Wilkes decided to pursue the British ship. On November 8, the San Jacinto intercepted the much smaller Thirty in the Bahamas Channel north of Cuba. Two warning shots persuade the British captain to allow the Union sailors to board his ship. They seized Mason and Slidell and then allowed Thirtyto continue his journey.

The question was what right Wilkes had to board and search a ship from a foreign country that was not at war with the United States. Wilkes, who was not trained as a lawyer, justified the interception to the Thirty Mason and Slidell’s furious captain constituted “contraband,” which made their seizure fair. This was an unprecedented legal interpretation. Worse still, Wilkes did not bring the Thirty himself to port, as required by international law, for a prize tribunal to rule on its decision to return the envoys. He ignored established legal procedure because the transfer of sailors to lead the Thirty would have left the San Jacinto dangerously understaffed.

When news of Mason and Slidell’s capture reached the North, Congress and the public hailed Wilkes as a hero. THE New York Times even suggested that the United States “dedicate another Fourth of July” in his honor. Some Union officials privately doubted the legality of Wilkes’ action, but Northerners looked for a reason to rejoice. Union forces had suffered a series of battlefield defeats, dashing hopes of a quick victory. Armed with the memory of two wars with Britain and numerous territorial disputes, many northerners also doubted whether London intended to honor its commitment not to participate in the rebellion.

The reaction in Britain was exactly the opposite. The government and public denounced Wilkes’ interception of a neutral ship traveling between neutral ports as a flagrant violation of maritime law. Foreign Secretary Lord John Russell angrily declared that “the world is disgusted by the insolence of the American Republic.”

London demanded the release of Mason and Slidell as well as a formal apology from the Lincoln administration for the Union insult to the British flag, or it would break relations with the United States. Such a move generally preceded a move towards war. To prepare for this eventuality, Britain put the Royal Navy on alert, sent 11,000 additional troops to Canada, and began preparing plans to break the Union naval blockade of the Confederacy. France announced that it would support Britain in its war against the United States.

Despite their belligerent attitude, neither the United States nor Britain were eager for war. But neither wanted to back down and lose diplomatic face. For a moment, war seemed certain. But shrewd diplomacy, the passage of time and other events cooled inflamed passions and allowed calmer heads to prevail.

As London formulated its ultimatum to Washington, Queen Victoria’s husband and closest advisor, Prince Albert, intervened to persuade the British cabinet to adjust its rhetoric. London’s softening of language gave Lincoln more freedom to respond to British demands than he might otherwise have had. The exchange of notes between the two capitals took time and allowed leaders on both sides of the Atlantic to assess the true cost of the war. The death of Prince Albert in mid-December after a long illness overshadowed the news of Thirty affair and ushered in a period of national mourning in Britain.

Lincoln recognized early on that the war with the British over the Thirty this affair would likely cost the Union victory in the Civil War. His war strategy relied on mobilizing the North’s superior industrial capabilities, fighting battles on Confederate territory, and maintaining a naval blockade that deprived the South of commerce and war materiel. War with Britain would likely mean a land attack on Canada, threatening the Northern economy and forcing the Union to divert its forces from fighting the Confederacy. The British Navy would also seek to break the Union naval blockade in the South, allowing the Confederacy to trade cotton for arms, while disrupting maritime commerce in the North, thereby sending its economy into a tailspin.

Faced with these facts, Lincoln decided, as he laconically put it: “One war at a time.” On December 26, his cabinet unanimously agreed to release Mason and Slidell. In the memo to the British announcing the news, Secretary of State William Seward did not admit that Wilkes had made a mistake in boarding the Thirty or by taking Confederate envoys prisoner. Seward instead argued that Wilkes’ failure to gain the upper hand Thirty before a prize tribunal, as dictated by international law, forced their release.

Showing a bit of diplomatic boldness, Seward also praised Britain for the position it had taken on the subject.Thirty affair. In doing so, he argued, London had accepted the long-standing American position on the right of neutral nations to conduct trade unhindered by warring nations, a position that Britain had resisted for decades and which had sparked the War of 1812. This diplomatic victory, many Northerners seemed to agree, was more important than the release of two Confederate envoys.

Happy to have forced the release of Mason and Slidell and avoided war, the British leaders pocketed their victory and ignored Seward’s provocation. The two Confederate envoys eventually reached Europe. However, they failed to obtain diplomatic recognition from the Confederation.

As the Civil War continued, Lincoln faced other foreign policy crises, including new disputes with Britain and French military intervention in Mexico. But he stuck to his decision to tackle one problem at a time and focused the Union’s efforts on defeating the Confederacy. It was a winning strategy.

Lincoln’s restraint and discipline offer a valuable lesson: The conflicts you avoid can be as important as the ones you make.

Oscar Berry and Jack Patton contributed to the preparation of this article.

The United States celebrates its 250th anniversary in 2026. To mark this milestone, I am drawing out essays I have written over the years on major events in American foreign policy. A version of this essay was published on November 8, 2021.