When we hear of filibusters, we tend to think of the political process used to stall legislation. The term is also used to describe individuals who take it upon themselves to wage war against other nations, outside of the activity of their own nation. Such a man was William Walker.

Walker began his filibustering career with an invasion of Baja California with an army of 45 men in 1853. Walker had negotiated unsuccessfully with the Mexican government to allow him to establish a military outpost to protect the southern border of California from Indian raids. The Mexican government, having recently lost California to the U.S., was in no mood to be cooperative. Walker’s invasion was initially successful, though with no official U.S. support, Walker was forced to retreat when the Mexican government responded with force.

In 1855, Nicaragua was embroiled in a civil war. Recognizing the commercial possibilities of the building of a canal in the area, Walker moved in. Receiving support from Francisco Castellón, leader of the Democratic party based in León, Walker took his “army” to Nicaragua. With support from other Americans in the area, Walker helped the Democrats when the war. He was eventually named president of Nicaragua. Walker dreamed of uniting all of Central America into one English-speaking nation.

Cornelius Vanderbilt, whose commercial interests were threatened by Walker’s work, helped mobilize the other Central American nations against Walker. He was ousted as Nicaraguan president in 1857 and was eventually executed in Honduras in 1860.

Walker’s work, especially the Mexican invasion, was completely against U.S. law, particularly the Neutrality Act of 1794 (forbidding U.S. citizens from waging war against a nation the U.S. was not at war with). Walker was tried for his crimes, but acquitted.

It’s easy to argue that no person better personified the doctrine of Manifest Destiny than Mr. William Walker.