Frederik Christian Kaas was the brother of. Their father was Admiral. In 1750 he was appointed as a gentleman at the Royal court. On 7 January 1765, he was married at Constantinsborg to Sophie Elisabeth Charisius who died only four years later. He later married again on 11 September 1771 in Bøstrup Church to Edele Sophie Kaas. In 1772, with an inheritance from his father-in-law, he bought an estate on Langeland.
Service career and promotions
From 1739 as a volunteer cadet, Kaas was officially accepted as a cadet in 1741 and sailed on the ship-of-the-line Oldenborg with the squadron to Algiers in 1747. In October 1747 he was commissioned as a junior lieutenant. Aspiring to become a master shipbuilder he joined the Construction Committee early in 1748, and from 1752 spent over four years along with lieutenant F M Krabbe studying methods of design and construction in England, France, Italy and Holland. Together, on their return to Denmark, the two young officers designed a Xebec and were to have started on a frigate but Kaas, having already had his first command in 1756 as captain of the frigate Hvide Ørn, was posted to the ship-of-the-line Neptunus and never continued his shipbuilding career. During this time Kaas was promoted twice. While Neptunus was in the Mediterranean both captain and second-in-command of the accompaying ship-of-the-line Island fell ill and died, so Kaas was appointed captain of Island and brought her back to Denmark in 1758. Confirmed in the rank of captain in December 1758, Kaas had command of various frigates over the next eight years, seeing service in the Baltic and Mediterranean and undertaking a diplomatic mission to Morocco in 1763 with the frigate Havfruen. A quarantine period for the ship returning from Salee, Morocco was applied when Havfruen stopped at Lisbon. In 1765 he led another mission to Morocco using an armed merchant ship specifically flying the danish royal standard. On return,in the spring of 1766, he was granted three month's special leave to order his personal affairs. 1767 Commander and in 1769 he became captain of the ship-of-the-line Mars. In this ship he carried the British Duchess of Gloucester from Copenhagen, where she had been visiting her sister, Queen Caroline Mathilde, to Mecklenburg in Pommerania. From 1770 to 1781 he was head of the naval officer training college, and after achieving flag rank in 1780 head of the naval base at Holmen from 1781 to 1792.
1792 Vice Admiral. As a deputy in the admiralty from 1792, Kaas became first deputy in 1796. With his rank he commanded a Danish squadron in 1995 1nd 1996 which operated alongside his Swedish counterpart in a neutrality patrol.Command of the joint squadron revolved half-yearly from the Swedish vice admiral to the Danish, and back
