In the early part of the nineteenth century there began to be formed in Spain secret societies for the purpose of advancing the cause of liberty and human progress. One of these associations, called _Caballeros Racionales_, became very influential, and corresponded with the society of the Grand Reunion of America (_Gran Reunion Americana_) of London. This society was pledged "to recognize no government in America as legitimate unless it was elected by the free will of the people." San Martin joined this society. The London society was established by Miranda, the Spanish patriot, a friend of Bolivar, by whose inspirations San Martin became a disciple of liberty, and whose dreams he fulfilled long after the patriot was dead. San Martin won honors and a medal in the Spanish resistance to the victorious eagles of Napoleon. In that campaign he fought under a banner of the Sun, having this motto in Latin: "We bear this aloft dispersing the clouds." He made this banner the flag of the army of the Andes. In 1812, San Martin, as a disciple of the principles of the Spanish apostle of liberty, Miranda, returned to South America, and in March went to Buenos Ayres, and offered his sword to the Argentine patriots for the cause of independence. The country was in revolution against the Spanish rule. San Martin was not only an American, but a Creole; he was unselfish, truthful, the soul of honor, and of all men in the world the one that would seem best fitted to lead the cause of the South American patriots. He was destined to become "the greatest of the Creoles of the New World." Soon after the arrival of San Martin in Buenos Ayres he married Doña Remedios Esculada, and Mercedes, a daughter of this marriage, shared with him his voluntary exile after the conquest of Peru. Appointed at once to a high military position under the Argentine Government, he conceived the plan of creating an army of the Andes, of crossing the Cordillera, and of driving the Spaniards from Chile. Mendoza, with which Buenos Ayres is now connected by railroad, lies on an elevation under the snowy Cordilleras. San Martin made his military camp here. On January 17, 1817, he began his march up the Andes, one of the most perilous achievements of modern warfare. The summit of the Uspallata Pass, over which the army was to climb, is 12,500 feet above the level of the sea, or 4,000 feet higher than the Pass of St. Bernard. The 17th, on which the army set forth, was a high holiday in Mendoza. The plaza was gay with banners, and the streets with patriotic decorations. The ladies of the city presented an embroidered flag to San Martin. The general, above whose head gleamed the snowy heights of the Andes, ascended a platform in the plaza, and waved this flag over his head, and shouted: "Soldiers, behold the first flag of independence!" There arose a great shout of "Viva la Patria!" "Soldiers, swear to sustain it." "We swear," answered the army, as one man.