Lacy's generous mind became deeply agitated at the prospect of being obliged to serve against that nation among whom his exiled family had found a home; and, notwithstanding the bitterness yet rankling in his mind against those who had treated him so ill in Spain, and who had dismissed him from the Regiment of Ulster, he determined not to draw a sword against the country of his father's adoption, and with sorrow sent his young wife, with their infant son, back to her family at Quimper, there to await the settlement of the Peninsular affairs. As _Chef-du-Battailon_, he still remained with the army which crossed the Pyrenees, in virtue of the base conspiracy of the Escurial, and which marched unmolested through the barrier-towns of San Sebastian, Figueras, Pampeluna, and Barcelona, in the spring of 1808; and in the summer of that year he found himself with the French army at Madrid. The events of the 2nd of May--the decoying of the Royal Family to Bayonne by Bonaparte--their compulsory renunciation of the Spanish crown--and other dark transactions, decided the noble Lacy on the course he should pursue. He relinquished his command of the Irish, and quietly quitting the capital, surrendered himself a prisoner of war to the venerable Spanish general, Don Gregorio de la Cuesta, who, in his seventieth year, still held the command of the forces to which Ferdinand VII. had appointed him, as Captain-General of Castile and Leon. Struck with the story and magnanimity of Lacy, and revering his character, Cuesta, the last of the old Spanish cavaliers, appointed him at once Lieutenant-Colonel-Commandant of the Battalion of Ledesma, which had been raised in the small province of that name, near Salamanca; and he gave all his energy and talent to discipline this regiment. For now Spain had risen bravely against the invaders, and the sturdy Asturians and Galicians, under Don Joachim Blake, a young officer of Irish parentage, had commenced the War of Independence. In all the operations of the Spaniards Lacy fought gallantly, at the head of his new regiment; but more particularly at Logrono, in Old Castile, and on the retreat to the Ebro, at Guadalaxara, thirty-two miles from Madrid; after the betrayal of which, the Spanish vanguard, which, under Venegas, had saved the army at Buvierca, by so bravely defending the pass, entered the city on the night of the 4th of December, 1809. The battalions (_tercios_) "of Ledesma and Salamanca, under Don Louis Lacy and Don Alexandro de Hore," skirmished for three hours with the French that night, on the banks of the Henares; but after a desperate encounter, the flower of the Spanish troops had to retire before them.