Walker now set out with his buccaneering band on a long march of six hundred miles through a barren and unpeopled country towards his "possessions" in the interior. The Mexicans did not need any forces to defeat him. Fatigue and famine did the work for them, desertion decimated the band of invaders, and the hopeless march up the peninsula ended at San Diego, where he and his men surrendered to the United States authorities. Walker was tried at San Francisco in 1854 for violation of the neutrality laws, but was acquitted. This pioneer attempt at invasion only whetted Walker’s filibustering appetite. Looking about for "new worlds to conquer," he saw a promising field in Nicaragua, then torn by internal dissensions. Invited by certain American speculators or adventurers to lend his aid to the democratic party of insurrectionists, he did not hesitate, but at once collected a band of men of his own type and set sail for this new field of labor and ambition. On the 11th of June, 1855, he landed with his small force of sixty-two men at Realijo, on the Nicaraguan coast, and was joined there by about a hundred of the native rebels. Making his way inland, his first encounter with the government forces took place at Rivas, where he met a force of four hundred and eighty men. His native allies fled at the first shots, but the Americans fought with such valor and energy that the enemy were defeated with a loss of one-third their number, his loss being only ten. In a second conflict at Virgin Bay he was equally successful, and on the 15th of October he captured the important city of Granada. These few successes gave him such prestige and brought such aid from the revolutionists that the opposite party was quite ready for peace, and on the 25th he made a treaty with General Corral, its leader, which made him fairly master of the country. He declined the office of president, which was offered him, but accepted that of generalissimo of the republic, an office better suited to maintain his position. His rapid success brought him not only the support of the liberal faction, but attracted recruits from the United States, who made their way into the country from the east and the west alike until he had a force of twelve hundred Americans under his command. General Corral, who had treated with him for peace, was soon to pay the penalty for his readiness to make terms with an invader. He was arrested for treason, on some charge brought by Walker, tried before a court-martial at which the new generalissimo presided, sentenced to death, and executed without delay. The next event in this fantastic drama of filibusterism was a war with the neighboring republic of Costa Rica. Both sides mustered armies, and a hostile meeting took place at Guanacaste, on March 20, 1856, in which Walker was worsted. He kept the field, however, and met the foe again at Rivas, on April 11. This time he was victorious, and the two republics now made peace.