In 1774, he obtained command of the expedition against Algiers. The great means of attack were entirely confided to him, and he sailed from the Spanish coast with a squadron of forty sail of the line and three hundred and fifty transports, carrying an army of thirty thousand men; but this immense armament failed to achieve its object, and O'Reilly was compelled to bear away for Spain, humiliated and mortified, and landed his discomfited troops at Barcelona, on the 24th of August in the same year.[17] Though this unfortunate result was much against his reputation as a general, it did not lessen his favour with the king, who placed him at the head of a military school which was established in Avila, at Puerto de Santa Maria, on the Adaga, in Old Castile. Soon after this, O'Reilly was named Captain-General of Andaluzia and Governor of Cadiz. In these important posts he displayed the talents of a skilful soldier and able administrator; but he fell into complete disgrace on the death of Charles III., in 1788, and lived afterwards in a quiet retreat in Catalonia. Despite his many enemies at court, who rose into power with Charles IV., O'Reilly maintained his high military reputation in the Spanish army, and on the death of General Ricardos in 1794, the government knew of none so able as he to direct the war against the invasion of the French republican armies. He was accordingly named General of the Army of the Eastern Pyrenees, and was on his way to assume that high command when he was seized by a sudden illness, and died in his sixtieth year. O'Reilly was fortunate, perhaps, in escaping thus the misery caused to Spain by the mistakes of the Conde de la Union, and the misfortunes consequent to reverse and defeat. His age would not have permitted him to sustain the fatigue of a war so active; and though he was the instructor of Blake and others who were esteemed the best officers of the Spanish army, as a foreigner he had many envious enemies, and all his ability as a soldier, with the sweetness and insinuating flexibility of his manner, was no guarantee to him among such a people as the Spaniards, who are ever cool and averse to strangers. His pupil, Joachim Blake, afterwards Captain-General of Aragon and four other provinces, was the son of an eminent Irish merchant who had settled at Velez, near Malaga, and was descended from an ancient family in the county of Galway. His mother was the daughter of a wealthy Spanish banker named Joyes.