As Sainte-Beuve indicates, the subject of the ‘Letters’ forms one of the episodes of the war between Spain and Portugal which followed as a consequence of the Restoration of 1640 and the achievement of the latter’s independence under the House of Braganza. This war, which lasted for twenty-eight years, until the final peace in 1668, was intermittent, and carried on only at long intervals owing to the state of the two contending parties. Spain had now entered on the period of her decline, and Portugal was in a hardly better condition after her sixty years’ captivity and the exhaustion of her forces which had taken place during the reign of Philip IV. Owing, however, to the aid of France, she had been enabled to hold her own up to 1659; but the news of the Peace of the Pyrenees seemed at first to take from her all hope of preserving her hardly won autonomy. Yet in spite of this, Mazarin, while signing the clause which bound France to abandon the Portuguese cause, determined, with his usual duplicity, that this should not prevent him from secretly aiding an ally whom he had found so useful in the past as a thorn in the side of Spain. Hardly, indeed, had the treaty been made than he began to occupy himself in recruiting for the Portuguese service a number of French officers whom the peace had left without employment. Among these the chief was Schomberg, who went to Lisbon in 1660 as commander-in-chief and to reorganise the Portuguese army. It was not, however, until 1663 that the hero of the Letters, Noel Bouton, afterwards Marquis of Chamilly and St. Leger, arrived in the country, which he was to leave four years later with the betrayal of a poor nun as his title to fame. For at the time when Schomberg was already there, we see Chamilly (as he is generally called) assisting at the marriage of his brother to Catherine le Comte de Nonant, referred to in the text (Letter II.). Three years afterwards, finding himself without military employment in France, he came to Portugal, attracted probably, like so many others, by the reputation of the great captain, with whom he had doubtless established friendly relations during the campaign in Flanders (1656-8).