Introduction

The Caroline affair (also known as the Caroline case) was a diplomatic crisis involving the United States, the United Kingdom, and the Canadian independence movement which lasted from 1837 to 1842. This modest military incident eventually acquired substantial international legal significance.

The affair began on 28 December 1837, when hundreds of Americans who had been recruited by Canadian rebel leader William Lyon Mackenzie encamped on Navy Island on the Canadian side of the Niagara River. They had been brought there by the small American steamer Caroline, which had made several trips that day between Navy Island and Schlosser, New York. Late that night, armed men crossed the Niagara River under British command to board and capture the vessel where it was moored at Schlosser’s Landing in US territory. Shots were exchanged and two US citizens were killed, a watch-keeper and a cabin boy. British forces set fire to the Caroline and set it adrift in the Niagara River, about two miles above Niagara Falls. Sensationalised accounts of the affair were published by newspapers.

The burning outraged civilians on both sides of the US-Canadian border. In retaliation, a private militia composed of both US citizens and Canadians attacked a British vessel and destroyed it. During 1838, there were several other clashes pitting British forces against private militia. The diplomatic crisis was defused during the negotiations of several US-UK disputes that led to the Webster-Ashburton Treaty in 1842. In the course of these negotiations, both the US and UK made concessions concerning their conduct.

Correspondence between US Secretary of State Daniel Webster and special minister to the United States Lord Ashburton outlined the conditions under which one nation might lawfully violate the territorial sovereignty of another state. The “Caroline test” (or Caroline Doctrine) states that exceptions do exist to territorial inviolability, but “those exceptions should be confined to cases in which the necessity of that self-defense is instant, overwhelming, and leaving no choice of means, and no moment for deliberation”.

According to scholars, the “Caroline test” remains an accepted part of international law today. For example, Tom Nichols (2008) has stated:

Thus the destruction of an insignificant ship in what one scholar has called a “comic opera affair” in the early 19th century nonetheless led to the establishment of a principle of international law that would govern, at least in theory, the use of force for over 250 years.

Background

The Reform Movement of Upper Canada in Ontario was a movement to make the British colonial administration in Canada more democratic and less corrupt. William Lyon Mackenzie was one of the key leaders of this movement. He was repeatedly elected to serve in a hostile parliament that repeatedly ejected him for his reform efforts. By 1837, Mackenzie had given up on peaceful means for reform and began to prepare for an uprising.

In December 1837, Mackenzie began the Upper Canada Rebellion by fighting the British in the Battle of Montgomery’s Tavern. His forces were seriously outnumbered and outgunned, and they were defeated in less than an hour. Mackenzie’s allies suffered another major defeat a few days later in London. After these defeats, Mackenzie and his followers fled to Navy Island in the Niagara River, which they declared the Republic of Canada on board the vessel SS Caroline.

Throughout these events, the Canadian rebels enjoyed widespread support from the Americans, who provided them supplies and bases from which to launch raids on the British.

Events

On 29 December 1837, Canadian loyalist Colonel Allan MacNab and Captain Andrew Drew of the Royal Navy commanded a party of militia that crossed the international boundary and seized the Caroline. They chased off the crew, towed the boat into the current and set her afire, then cast her adrift over Niagara Falls. A watchmaker named Amos Durfee was shot and killed in the process.

British diplomat H. S. Fox summarised the British justification for the incursion in an 1841 letter to John Forsyth:

The steamboat Caroline was a hostile vessel engaged in piratical war against her Majesty’s people … it was under such circumstances, which it is to be hoped will never recur, that the vessel was attacked by a party of her Majesty’s people, captured and destroyed.

New York’s response (Willis Hall, Attorney General of New York on the Caroline Affair):

Those of our fellow citizens … single-handed and alone, left our territory and united themselves with a foreign power, have violated no law … they have done no more than has been done again and again by the people of every nation. Your own recollections of history will furnish your minds with hundreds of examples. The Swiss nation have, for hundreds of years, fed all the armies of Europe; and who ever thought of holding them responsible for it? They did no more than Admiral Lord Cochrane did in taking part with South America. They did no more than Lord Byron did, who gave his life to aid the Greeks in breaking the chains of Turkish bondage. They did no more than Lafayette. Gentlemen, I am not deviating from the case further than is necessary to remove the just odium which has been unjustly thrown upon those who joined the insurgents.

US newspapers falsely reported “the death of twenty-two of her crew” when only Durfee was killed. Public opinion across the United States was outraged against the British. President Martin Van Buren protested strongly to London, but was ignored.

Aftermath

Canadian sheriff Alexander McLeod claimed that he helped attack the Caroline during the affair, and he was arrested in the United States in 1840 for his role in Durfee’s death during the attack. This caused yet another international incident, as the British demanded his release, stating that he should not be held criminally responsible for following orders. The trial attempted to identify who shot Durfee, but this proved futile. McLeod was acquitted of all charges, as witness statements made it clear that he had no involvement in the incident.

Many towns bordering Canada insisted that the United States enter a war with Britain because of this incident, while Canadians celebrated it and MacNab was knighted for his efforts.

A band of 13 men captured and burned the British steamer Sir Robert Peel while she was in American waters. President Van Buren sent General Winfield Scott to prevent further incursions into Canada.

This incident has been used to establish the principle of “anticipatory self-defense” in international politics, which holds that it may be justified only in cases in which the “necessity of that self-defence is instant, overwhelming, and leaving no choice of means, and no moment for deliberation”. This formulation is part of the Caroline test.

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