The spirit of the warrior and patriot was stirred within him by the struggle of the Texans for independence, and he raised a voluntary force to join in that contest. Of this regiment thus voluntarily raised, he became the lieutenant-colonel. The command marched westward, shared in the battles of that land of plains, and returned when the struggle was ended. Again entering politics, he represented his county in the legislature of Alabama, where he won distinction as a debater and statesman, and later he became a Democratic elector in a presidential contest. In all these stations Colonel Clemens showed more than ordinary ability and won a degree of distinction. Having gotten a taste of war in the struggle in Texas, he was again induced to employ his sword in the Mexican War. Becoming lieutenant-colonel of the Ninth Infantry, his command participated in a number of battles in Mexico. In 1849 he was appointed governor of the civil and military department of purchase in Mexico. In this connection he served till the close of the war with Mexico, after which time the army was reduced and Colonel Clemens returned to Alabama and resumed the practice of law. Vast opportunity had thus been afforded this gifted man for the enlargement of his vision of affairs, and it had not been slighted. His military career had served to bring him into increased conspicuousness and to enhance his popularity. When Hon. Dixon H. Lewis died in New York, Colonel Clemens was elected to fill his unexpired term.