During the War of the Bavarian Succession, he joined the volunteer corps as a Captain, fought with distinction against the Austrians and was soon promoted to Major.

With the improvement of Prussia's relations with England, which occurred in the last years of Frederick's reign, Lusi managed to exert a more fruitful ambassadorial activity.

He was recalled in October 1788 from London, and in 1790 he accompanied the new king, Frederick William II, who contracted an army against Austria.

In January 1792 he had a son, Friedrich Wilhelm Ludwig August Spiridion (Φρειδερίκος Λούζης),[1] who would eventually become captain in the Guards Regiment.

The name died out in Ireland in 1919 with the death of his granddaughter Countess Elise de Lusi, but his other Irish descendants include the physicist Professor John Joly FRS (1857–1933).