"Intercourse … of the Most Friendly Nature": The U.S. Navy, State Power, and William Walker's Invasion of Mexico, 1853–1854

This article examines federal officials' attitudes towards illegal filibustering expeditions, using as a case study the U.S. Navy's role in defeating William Walker's 1853–1854 expedition to Baja California and Sonora, Mexico. The officers of the U.S.S. Portsmouth (especially former Democratic newspaper editor Levi Slamm), fraternized with filibusters, evacuated their wounded, and published expansionist sentiments. Yet even expansionist officers generally disapproved of filibustering's lawlessness and tendency to damage America's reputation and diplomatic attempts to buy territory legally. This article uncovers how many apparently sympathetic actions by officers and other frontier officials were actually covert and indirect anti-filibustering tactics that they adopted to compensate for local sympathy for the invaders, lack of support from Washington, and poorly defined (or nonexistent) authority to act more decisively. Although these tactics could subvert individual filibustering expeditions like Walker's, by not openly and directly opposing filibustering, they undermined U.S. diplomatic and political aims in the long term.