Final answer:
During the antebellum era, filibuster expeditions were unauthorized military endeavors undertaken by private individuals to annex new territories as slave states and expand the American empire of slavery. They were motivated by a belief in White racial superiority and were conducted despite being illegal and opposed by the government.
Step-by-step explanation:
The Filibuster Expeditions of the Antebellum Era
During the antebellum period, various schemes were pursued to expand the territory favorable to slavery in the United States, one of which involved filibuster expeditions. Contrary to government policy, these were private military expeditions led by individuals known as filibusters. Their goal was to annex new territories to create additional slave states and thus expand the American empire of slavery. Notable among the motivations for these filibusters was a belief in White racial superiority as they sought to extend territories conducive to their socio-political interests.
In 1819, for example, an armed group of two hundred Americans launched an expedition to Spanish Texas, intending to establish a republic. However, they were expelled by Spanish forces. This incident underscores the reality of such expansionism and the eventual federal crackdown on such activities. President Andrew Jackson's military prowess highlighted the American spirit of these ambitions. Later, the publication of the Ostend Manifesto intensified the debate around seizing Cuba, leading President Pierce and his successor President Buchanan to renounce filibusters, whom Buchanan labeled as pirates. Despite legal measures against them, filibustering persisted, driven by the ideology of manifest destiny and southern interests in preserving and spreading the institution of slavery.
Though today the term filibuster is more commonly associated with legislative obstruction, back in the antebellum era, it was synonymous with bold, yet illegal, military aggression aimed at territorial expansion under a racially charged agenda. This chapter in U.S. history highlighted the intense divisions over the institution of slavery that would eventually contribute to the onset of the Civil War.