Ironically, if the sectional quarrel had not overshadowed all other events, Buchanan might be remembered as a bold and vigorous imperialist, in part for his role in co-authoring the Ostend Manifesto. Futher, in a special message to Congress in 1858 he concluded, "It is, beyond question, the destiny of our race to spread themselves over the continent of North America, and this at no distant day."
In 1857 he ordered twenty-five hundred troops under Colonel Albert Sydney Johnston to suppress the Utah Mormons, and only the heroic work and tact of Thomas L. Kane brought the Saints into sufficient submission to avoid a bloody war. Buchanan publicly condemned the filibustering efforts of William Walker in Central America, but the Department of State released Walker, and Buchanan reprimanded Commodore Hiram Paulding for using armed force in the territory of a friendly nation, Nicaragua, while making the arrest. Walker later insisted that Buchanan had offered him secret encouragement, and Nicaragua angrily denounced the president for Walker's activities.
Buchanan boldly defied the British in several controversies. Fortunately, Disraeli and other British leaders had concluded that American control of Central America might increase the productivity of the region and thereby expand the market for British goods. Under Buchanan's pressure, the British made sweeping concessions to local government in the area. Relations with Britain were further complicated by British efforts to stop the African slave trade. Though committed by treaty to assist in this effort, the American government admitted no right of search in peacetime, and most slavers, regardless of nationality, would raise the American flag when British ships appeared. In 1858, when the British sent a small fleet to Cuba and the Gulf of Mexico, Buchanan, with full Senate support, ordered every available vessel to the Gulf "to protect all vessels of the United States . . . from search or detention." Rather than risk war, the British stopped their efforts against ships flying the American flag. In the Northwest, in 1859, a quarrel with Britain over the ownership of San Juan Island ended in a complete American victory after Buchanan sent a naval force and a small army under General Scott to the area.
Annually, Buchanan asked Congress for troops to quell lawlessness and protect travelers in Central America. Congress refused, but the president persuaded both New Granada (now Colombia) and Costa Rica to acknowledge claims against themselves. He bullied Nicaragua into granting transit rights and induced Mexico to grant the right of military occupation in case of disorder. Mexican civil wars continued to take American lives and property, and in 1858, Buchanan asked Congress for authority to assume a temporary military protectorate over northern Mexico. The Senate Foreign Relations Committee approved, but the full Senate refused. In December 1859 the president asked for authority to invade Mexico and obtain "indemnity for the past and security for the future." Fortunately for Mexico, Congress was entirely occupied with John Brown's raid. In 1860 the administration signed a treaty in which Mexico sold the United States transit rights and the right to police the route, but again the Senate balked.
In February 1855 an American helmsman had been killed on the Paraná River by gunfire from the shore. Three years later, Buchanan sent a commissioner with a commodore, nineteen warships, and twenty-five hundred marines and sailors to Paraguay. The expedition collected $10,000 in damages for the sailor's family, an apology, and a useless treaty of trade and commerce. Meanwhile, every effort to get money to buy Cuba or take it by force also fell victim to the slavery quarrel.
If James Buchanan really meant everything he said and really wanted everything he requested from Congress, he was prepared to annex everything from the Rio Grande to Colombia at the risk of war with nations involved or with Great Britain, if necessary. Threatening weaker Latin neighbors may not have required great courage, but if the British had stood their ground in Central America and had defended their right to search suspected slave ships, Buchanan might have had to choose between war and a humiliating retreat. Conceivably, he may have considered such tactics a possible tool for achieving unity between the quarreling sections—Seward would later recommend this to Lincoln—but if so, he was strangely blind to the harshly divisive impact of both the War of 1812 and the Mexican War.