American Filibusters 1850–1857: How Private US Armies Invaded Central America

American filibusters were private armed bands from the United States that invaded neighboring countries in the 1850s to seize power there. Cuba, Mexico, Nicaragua, Honduras — for example. Officially, Washington had nothing to do with them. In reality, however, they were sent off as heroes, and courts let their leaders go in a matter of minutes. So today I will tell you how this system worked.

The word “filibuster” came from Spanish and Dutch — it meant sea robbers. Then, in mid-19th-century America, it was applied to adventurers who raised armies and set off to conquer other people’s lands. And do you know the most disgusting part? This was not the private initiative of loners at all, but, in essence, policy. Behind them stood money, newspapers and politicians.

Where American filibusters came from

Let’s start with ideology. In the 1840s the US gave birth to the doctrine of “Manifest Destiny”: supposedly God himself wanted Americans to own the continent. After the war with Mexico, which ended with the US taking about half of Mexican territory, the appetite only grew. As a result, the next targets were Cuba, Central America and what was left of Mexico.

In addition, this expansion had a very concrete engine — slavery. The Southern states wanted new lands where slaves could be held. Moreover, every new slave state gave the South votes in Congress. Therefore planters gladly paid for expeditions that promised to “liberate” neighboring countries and in fact to open a slave market there.

Formally, though, all of this was illegal. Since 1818 the US had a Neutrality Act that banned raising armies on its soil for war against countries at peace. However, the law worked only on paper. Meanwhile bands openly recruited men in New Orleans, San Francisco and New York, and the authorities looked the other way.

Cuba: the expeditions of Narciso López

The first big name was Narciso López, a former Spanish general who decided to “liberate” Cuba with American help. In May 1850 his band of about 600 men landed in Cuba and took the town of Cárdenas. However, the support of local people never came, and he fled back to Key West.

By the way, the money for these raids came from Southern slaveholders. It suited them for Cuba, with its sugar plantations and hundreds of thousands of slaves, to become an American state. In August 1851 López tried again, but the Spanish crushed the band. López was executed by garrote in Havana, and about 50 American volunteers were shot along with him.

American filibusters in Mexico and Nicaragua

In 1853 a man entered the game whose name would later become the symbol of the whole era — William Walker. First, with a small band, he invaded Mexican Baja California and declared a “Republic of Lower California” there, then added Sonora to it as well — on paper. Nevertheless, the Mexicans drove him out in May 1854.

This is where the most telling part begins. Back home, Walker was tried for violating the Neutrality Act. The jury deliberated for about eight minutes and acquitted him. In other words, American society made it clear: you can invade a neighboring country if you are one of us.

Just a year later Walker landed in Nicaragua. Then he seized power, proclaimed himself president, brought back slavery — and the Franklin Pierce administration recognized his government. That is a separate story, and I look at it in detail in the article about William Walker in Nicaragua. I will only say that in the end his war cost Central America thousands of lives.

Greytown: when the navy stood up for the filibusters

Don’t think the state only turned a blind eye. In July 1854 the American sloop Cyane approached the Nicaraguan port of Greytown (San Juan del Norte) and shelled it. Then the Marines landed and burned what was left. The pretext was a quarrel between local authorities and an American transit company and an insult to an American diplomat.

Thus an entire town was wiped off the face of the earth over the interests of one company. Moreover, the residents never received any compensation. At the same time, in that same year of 1854, American diplomats signed the Ostend Manifesto — a document that said plainly: if Spain will not sell Cuba, it can be taken by force. So the difference between “private adventurers” and the state was very thin.

American filibusters in Sonora: the end of Henry Crabb

Finally, the last major raid of that wave was Henry Crabb’s march into Mexican Sonora in the spring of 1857. The former California politician led a band there, counting on the support of local factions. However, the Mexicans surrounded him near the town of Caborca. In April 1857 Crabb and most of his men were shot.

What American filibusters brought to the region

To sum up, American filibusters left scorched earth behind them. In the war against Walker alone, the countries of Central America lost about 5,680 people killed and wounded. In Costa Rica a cholera epidemic broke out, which took 9,615 lives in ten weeks. And all this so that a handful of adventurers and planters could get new slave lands.

Nevertheless, in US textbooks this era is still presented almost romantically: brave adventurers, the frontier spirit. Frankly, this romance makes me furious. After all, not one of the leaders ever answered for the blood before an American court. Only those who were caught in foreign countries had to answer.

Mercenaries instead of an army: the method lives on

And don’t tell me this is all long in the past. The principle American filibusters followed — fight with the hands of private individuals so the state can say “we have nothing to do with it” — is alive today. In 2007 guards of the American private military company Blackwater shot 17 Iraqi civilians in Nisour Square in Baghdad. Later the convicted men were pardoned by a US president.

Or, for example, Venezuela, May 2020. A group of mercenaries led by a former American special forces soldier from the firm Silvercorp tried to land in the country to capture President Maduro. The operation was called “Gideon”. Washington, of course, declared it had nothing to do with it — word for word as in the 1850s. And in 2025 the US was already openly sinking boats off the coast of the same Venezuela and bombing Iran without declaring war.

In other words, only the signboards change: back then “liberation expeditions”, today “private contractors” and “fighting threats”. The essence is the same — foreign land, foreign lives and American interests. You can read more about the phenomenon itself in the article on filibusters. And about how this line continued at the hands of the state itself, I wrote in the pieces on US interventions in Nicaragua, on the “Christmas coup” in Honduras and on the William Eaton expedition — the first American operation carried out by mercenaries.