He first appears in the history of the country in the Mexican war, is present at the bombardment of Vera Cruz, dashes after the enemy at Cerro Gordo, capturing on the crest of the hill a battery which he turns upon the discomfited foe. At Contreras his command proves as impenetrable as a phalanx of Alexander; and when at last the victorious Americans fight their way into Mexico, the city of fabulous treasures and associations well-nigh classical, for the first time he receives a wound. He was breveted captain for his gallantry at Cherubusco, and at the end of the war received the rank of full captain, and was ordered with his regiment to California. No appointment could have been more felicitous. In the guerilla mode of warfare demanded by the peculiar nature of the country and its inhabitants, his habits of quick decision, and the experience of a war with an enemy equally unscrupulous though less undisciplined, were absolutely invaluable. Here was no scope for the conception and excitation of deep-laid schemes; the movements of the enemy were too rapid. Plans that would elsewhere have been matured only in the process of a long campaign, were here often originated and completed in a single night. Simple strategy was of more avail than the most intricate display of military science, and the impulse of a moment more to be relied upon than the prudent forethought of a month. He had to combat, in the newly-acquired territory, the cunning of tribes whose natural ferocity was sharpened into vindictiveness by the encroachments upon their soil of a new and strange people; and every association with the intruders, who were for the most part men of little reputation and less principle, had developed in the Indians only the fiercest and most decided animosity. To encounter their vigilance with watchfulness as alert, to confound their swift counsels with sudden alarm, to penetrate their ambuscades and anticipate their cunning with incessant activity, to be, in short, ubiquitous, was the duty of Captain Lyon.