As the third son of a cadet (junior) branch of the Fürstenberg princely family, Karl Aloys was prepared for a military career. His tutor, Lieutenant Ernst, was in active service in the Habsburg military, and took six-year-old Karl Aloys on maneuvers with him. In this way, he learned as a child the Habsburg military manual, and came into contact with important military men who later furthered his education and career; he also acquired an honorary rank as "Kreis-Obristen", or Colonel of the Imperial Circle, by the time he was ten years old. As a youth, in 1776, he met the Habsburg war minister Count Franz Moritz von Lacy and Baron Ernst Gideon von Laudon; he was also invited to dine with Emperor Joseph II. He started his service in 1777 as a "Fähnrich" (ensign) in the Habsburg military organization. He saw his first field service during the War of the Bavarian Succession (1777–78), although he was not involved in any battles.