As a French officer, Nassau-Siegen failed in his hastily prepared attack on the isle of Jersey (1779). For commanding the fireships at the siege of Gibraltar, Nassau-Siegen received from Spain three millions of francs and the dignity of Grandee of Spain. At Spa he met his future wife, Polish Countess Karolina Gozdzka, who was recently divorced Prince Sanguszko and the owner of a small estate in Podolia, then in the Polish–Lithuanian Commonwealth.