Monday, September 22, 2025

USA spies: From the American Revolution to the Civil War



“Therefore no one in the armed forces is treated as familiarly as are spies, no one is given rewards as rich as those given to spies, and no matter is more secret than espionage.”

– Sun Tzu’s “The Art of War” (5th century BC China), Chapter 13 (as translated by Thomas Cleary)

Information traveled slowly in those days, at the speed of a horse or a sailing ship

Sun Tzu reminds us that spies have been around since antiquity. In the Peloponnesian Wars of Ancient Greece, for example, Alcibiades betrayed Athens to Sparta, then defected to the Persian side, and then returned to Athens. This high-profile treason had a way of making him a little unpopular in certain quarters, to say the least. But most of the glory of espionage tends to go to the later Cold War period of the twentieth century. The latter period has been the subject of movies like “Breach,” “Bridge of Spies,” and (of course) the “James Bond” franchise. We may thus tend to associate spies with high-tech methods, like hacking and computer encryption. But most of the spies in history were somewhat lower-tech, and the embarrassing government secrets could travel no faster than the speed of a horse. And, during the American RevolutionLondon and Paris were way across the ocean from the critical campaigns in North America. Thus, it could take months for important information to sail across the Atlantic. The news of the American victory at Saratoga took several months to bring France into the war, delaying the all-important French assistance to the outnumbered (and badly outgunned) American rebels.


British surrender at Saratoga, 1777

Some information in this post was once top-secret, while the rest is largely forgotten

But the spy conflicts of the early United States are largely forgotten today. We hear much about the American Revolution and the Civil War in school, but we don’t hear too many stories about the important spies in our earliest conflicts. This is understandable, because the discussions of these wars usually have to focus upon the politics involved therein – and, of course, upon the many battles themselves. But the spy stories of these wars seem to have all the drama of more modern spy conflicts. They have all of the human interest, all of the juicy scandals, and all of the broader strategic importance. Specifically, the spies therein had a great effect on how these wars ultimately played out. Thus, this might be a good time to talk about a few of the spies in America’s earliest conflicts. Some of the information herein was once top-secret. The rest is largely forgotten to the public. But these details tell a story about how the military secrets of both sides were either protected, or (more embarrassingly) leaked – sometimes with catastrophic consequences, for the one side or the other.


Paul Revere’s ride


The rebels of the American Revolution are now known to history as the “Patriots” …

By historical convention, the Americans who rebelled against Great Britain are now known simply as the “Patriots.” But a great many Americans were instead affiliated with the “Loyalist” side – that is, the side that remained loyal to the British. It has been estimated that roughly one-third of Americans supported the Patriot side, that another one-third of Americans supported the Loyalist side, and that the other one-third supported … whoever then happened to have control in their area. These divisions within the population had important consequences for the era’s espionage. It meant that both sides then had plenty of people in North America who were willing to spy for them. On the Patriot side, Paul Revere famously alerted the colonials to how “The Redcoats are coming!” This played an important role in the first battle of the war at Lexington and Concord. The Continental Congress also created a “Secret Committee,” a “Committee of Secret Correspondence,” and a “Committee on Spies.” During the early campaigns in New York City, Nathan Hale also spied for the Patriots. Unfortunately for the Patriots, though, Nathan Hale was captured by the British and hanged. It has traditionally been reported that Hale’s last words were as follows: “I only regret that I have but one life to lose for my country.” Then as now, spying could be a little risky for those involved.


Nathan Hale, a Patriot spy who was hanged by the British

… but many Americans were affiliated with the “Loyalist” (or pro-British) side of the war

Benedict Arnold was originally affiliated with the Patriot side. But he soon married into the Loyalist family of Peggy Shippen. Thus, he eventually started to work for the British side instead – and his name has since become synonymous with “traitor.” He agreed with a British officer, Major John André, to turn West Point over to the British. They used a book cipher – possibly based upon Sir William Blackstone’s “Commentaries on the Laws of England,” incidentally. But, unfortunately for the British side, the plot was soon discovered, and some of the spies were caught. Most prominently, British Major John André was hanged by the Patriot side. But Benedict Arnold actually managed to escape from his former allies. Thus, Benedict Arnold served on the Loyalist side of the war from then on. This was probably the most prominent Loyalist espionage of the American Revolution, although Charles Lee was also a prominent traitor in that war. Spying played a role for both sides in North America. But, in ParisBenjamin Franklin was trying to get the French to enter the war. In every stage of his diplomacy, there were British and Loyalist spies in Paris (not to mention local French spies), trying to find out everything about his operations. Benjamin Franklin knew that it was useless to try to keep the spies away from him. There were so many of them that this would have been an exercise in futility. Thus, Dr. Franklin said that if he had known his valet to be a spy, he “wouldn’t have dreamt” of discharging him (to paraphrase what he said) – if the man was a good valet. But Dr. Franklin proved good at deceiving the British, and communicated with the Continental Congress in prearranged ciphers. The British also used ciphers in Paris. Thus, we can only guess as to the meaning of certain words, from the surviving diplomatic documents of this time. They are still unknown to this day.


Benedict Arnold, the most infamous traitor of the American Revolution


John André, a British spy who was hanged by the Patriots

Spies in the Anglo-American “War of 1812,” and in the years leading up to it

Relatively little information is publicly available, about the spying in the War of 1812. Wikipedia has a page on “Intelligence in the American Revolutionary War” (available here) However, they currently lack a page on spies specifically in the War of 1812. Thus, I will instead turn to their page on the “History of espionage,” which has a related section. Specifically, they say that “The Kingdom of Great Britain, almost continuously at war with France (1793–1815), built a wide network of agents and funded local elements trying to overthrow governments hostile to Britain.” (Source: Section on “French Revolution and Napoleonic wars, (1793–1815)”) This page also notes that “Britain in 1794 appointed William Wickham as Superintendent of Aliens in charge of espionage and the new secret service. He strengthened the British intelligence system by emphasizing the centrality of the intelligence cycle – query, collection, collation, analysis and dissemination – and the need for an all-source centre of intelligence.” (Source: Section on “French Revolution and Napoleonic wars, (1793–1815)”) This would have important consequences for the distant war in North America. But this is the closest that Wikipedia comes to coverage of the spying in the Anglo-American War of 1812. Thus, I should mention that this again occurred in an international context. The United States was again allied with France, which was now led by Napoleon Bonaparte. As in the American Revolution, Canada was still a part of the British Empire. There were a number of Canadians that spoke French as their native language. But most of the British and Canadians spoke English: the same language as the Americans. This would have important consequences for both sides’ spy efforts in North America. That is, it made it somewhat easier for the two sides to spy on each other. There were also Canadians of American origin. Some of them had Loyalist ancestors from the American War of Independence, but others remained sympathetic to the United States. Some of them even helped out the United States when the Americans invaded Canada. This would be important in how the war turned out.


William Wickham, British spymaster in the years immediately preceding the War of 1812

Spies in the Mexican-American War of the 1840s, including in the Republic of Texas

But let me now turn to the Mexican-American War of the 1840s. In the years leading up to the war with MexicoTexas was an ethnic mix. That is, there was Gringo immigration to Mexican-controlled Texas, much of which was illegal. (More about that here.) Thus, Gringos eventually became the dominant group in Texas, even while it was still a part of Mexico. This meant that, in Texas, there were already plenty of people willing to help the United States government with information. This would have important consequences for the intelligence-gathering in the Mexican-American War. Obviously, there was a language barrier between the United States and Mexico in the war. Specifically, the Gringos spoke English, while those from Mexico tended to speak Spanish. This made it somewhat harder for both sides to spy on each other. But we nonetheless know that the locals could be important sources of information in this war. As the United States Army got deeper into Mexican territoryMexico seems to have had something of an advantage in this area. This was simply because more of the locals sympathized with their native Mexico. But, then as now, spy services could sometimes be purchased with sufficient money. This helped the United States somewhat, although it is hard to know exactly how much. However, we know that Anna McClarmonde Chase (better known as “Ann Chase”) was spying for the United States in this war. Interested readers are referred to Wikipedia’s page on Ann Chase for more information. As you may know, the United States acquired a significant amount of territory from Mexico in this war. But its attention would soon be turning to an upcoming civil war instead.


Anna McClarmonde Chase, an American spy during the 1840s war with Mexico

In the American Civil War, spies were everywhere, and “habeas corpus” was suspended

When the American Civil War broke out in 1861, spies from both sides were everywhere. As with the American Revolution, there was a division of the population – particularly in the border states. There were enough Confederate sympathizers in Maryland that they actually proved a threat to Washington DC itself. This is why the Lincoln administration temporarily suspended habeas corpus, and threw the rebels there in prison for the duration of the war. To me, this was a necessary war measure for protecting the Union capitol, and so was dispensing with trying them in court – the definition of suspending “habeas corpus.” Indeed, the United States Constitution says that “The privilege of the writ of habeas corpus shall not be suspended, unless when in cases of rebellion or invasion the public safety may require it.” (Source: Article 1, Section 9, Paragraph 2) Obviously, the Civil War was a case of “rebellion or invasion,” and the public safety seems clearly to have required these exceptions. Thus, the exceptions made here by Lincoln … were clearly constitutional, and were mostly limited to the border states anyway. I might also note that the Confederate capitol of Richmond was only a hundred miles or so from Washington DC. There was a real threat from Southern invaders as well. As in the American Revolution, both sides tended to speak English, which made it ridiculously easy for them to spy on each other. Southerners had an accent different from that of the North, but both sides could sometimes fake accents when they needed to do so. And there were some White Southerners who were willing to help the North, in the so-called “Kingdom of Jones.” People’s loyalties often had more to do with ideology (or, in some cases, money) than they did with the regional origins indicated by their speech. In the North, Rose O’Neal Greenhow was a Confederate spy. So was Belle Boyd, better known as “La Belle Rebelle.” She passed some damaging information on to the Confederacy.


Rose O’Neal Greenhow, a Confederate spy


Belle Boyd (a.k.a. “La Belle Rebelle”), another Confederate spy

Slaves were often the best spies of the war, and sympathized with their Union liberators

During the war, the Confederates invaded the North a few times. They even made it as far as the Pennsylvania town of Gettysburg. This meant, at those times, that most of the locals sympathized with the Union, and provided the Union armies with information. But most of the war, as you might expect, instead took place in the South. This meant that most of the White locals were willing to provide the Confederates with information. But the Black locals were another matter entirely. Enslaved African Americans tended to sympathize with the Union, and thus happily provided the Union armies with any information that they needed. It is more than mere “political correctness” to say that they were often the best spies of the war. They knew the local geography, among other things, and were willing to tell their liberators anything that they wanted to know about it. Harriet Tubman herself had been involved in the “Underground Railroad” since before the war. In the prewar days, this group had helped some runaway slaves to escape to the North. During the war, it was also helping some Confederate secrets to find their way to the North. In many ways, this proved important in the ultimate outcome of the war. More about that in a Wikipedia page on “American Civil War spies,” which is available here. But relatively little information is readily available, about espionage in the later Spanish-American War of 1898. The Spanish-American War, after all, lasted for only six months. But the later wars of the twentieth century obviously took place in a much more international context. Thus, they might deserve a separate post of their own. Therefore, I have written such a post – which is available here, for any that are interested. I will offer that as a sequel to this post. More about that later.


Allan Pinkerton, a Union spy during the Civil War


Harriet Tubman, a Union spy during the Civil War

Conclusion: Spies played an important role in all of America’s earliest conflicts

Thus, spies played an important role in all of America’s earliest conflicts. The divided loyalties of the local populations sometimes had their effects upon the spy war, as they did upon the larger shooting wars – of which they formed an important part. The Mexican-American War and the Spanish-American War both saw language barriers which interfered with both sides’ espionage. But most of our other wars saw two sides which (mostly) were speaking the same language, and tended to have largely the same traditions – and even religions! This often made it easier for these two sides to spy on each other. The espionage in our earliest conflicts may not enjoy the glory of the spying in the World Wars, or in the later Cold War. But this espionage did play an important part in early American history, and in the broader history of the world at large. And it provides some juicy stories rife with human drama, which are quite fascinating in their own right.

Footnote to this blog post:

For more about spying in the two World Wars, see this blog post. And, for more about the iconic spying of the Cold War, see this blog post.

Disclosure: I am an Amazon affiliate marketer, and can sometimes make money when you buy the product using the link(s) above.

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