When the Mexican War began Semmes served under Commodore Conner at Vera Cruz, where he was in command of a battery of breaching guns. Throughout the war with Mexico, he served in the American fleet. After the declaration of peace, he was made inspector of lighthouses on the Gulf of Mexico, and in 1858 he rose to the position of a commander in the fleet, and was made secretary of the lighthouse board, with headquarters at Washington. Resigning his position when Alabama seceded from the Union, he repaired to Montgomery, the first capital of the Confederacy, where he was made commander of the Confederate navy. With the "Sumter," which Secretary Mallory had named in honor of the first victory of the war, Semmes began his "services afloat." The "Sumter" was a slender vessel and one of small capacity, but it was all that could be practically called the Confederate navy. But with this light cruiser, Semmes scoured the seas, and within a few months captured seventeen merchant vessels, after which the small vessel was disposed of, and Semmes having the "Alabama," a real gunboat for that time, built in England, and secretly sent to the Azores Islands, he assumed command of it and began in real earnest an offensive warfare on the high seas. He wrought rapid havoc with his little gunboat, burning fifty-seven of the enemy's ships and releasing many others on ransom bond. There being no ports open for condemning, Semmes burned his captures as permitted by international law. Dashing here and there over the deep, the operations of the "Alabama" were a series of brilliant exploits which attracted the attention of the world. Now at the Azores, again within two hundred miles of New York, then appearing unheralded in the regions of the West Indies, he suddenly appears in the waters of the Gulf off Galveston, Texas, sinks the federal steamer "Hatteras," capturing and paroling the crew, then dashing away to the coast of South America, he crosses the Cape of Good Hope, sweeps over the Indian Ocean, and in his work goes half way round the globe. That which was being done by the most daring and dashing commanders on land, was being done by Semmes on the high seas. Swift and tactical, he would appear at the most unsuspected time and in the most unconjectured quarter, and spread terror and destruction. For three years, Semmes roamed the seas of the world uninspired by the press and people of the South, for his deeds of daring were unknown, by reason of the blockaded ports of the Confederacy, and yet single-handed the little gunboat accomplished results that were wonderful. The story of a phantom ship ploughing the seas and accomplishing amazing feats, could scarcely be more romantic than was that which was actually done by Semmes and his little gunboat.