It was to be expected, perhaps, that the systematic reduction of the practice of nations in the conduct of war to legitimate rules should emanate from the camp rather than from the cloister. Accordingly we find a treatise by Balthasar Ayala, the judge advocate of the Spanish army in the Netherlands, dedicated in 1581 to the Prince of Parma, under whom he served. To this work we may refer, as the opening of a great subject on a basis strictly within the province of international jurisprudence, and disconnected from theological casuistry.
Ayala lays down the general principles upon which the right of hostilities rests, without subtlety or chicanery. Victoria had maintained that necessity alone can justify a declaration of war, and that when war has been declared for a just cause, it should be carried on, not with a view to destroy the enemy, but in order to secure a durable peace. Ayala proceeds to show that a war is just which is undertaken for the defence of a state, its subjects, its property, or its allies, or for the recovery of what has been carried off by an enemy; and Mr. Hallam has observed, with good reason, that Grotius, who refers to Ayala with commendation, is mistaken in saying that Ayala has not touched the grounds of justice and injustice in war. “Causas, unde bellum justum aut injustum dicitur, Ayala non tetigit.” (Prolegomena, § 38.) Ayala, with Victoria, explicitly denied the right of levying war against infidels, even by the authority of the Pope, on the mere ground of religion, as their infidelity did not deprive them of the right of dominion, which they possess by the law of nations.
Allusion has been already made to the influence of the Reformation upon the system of European jurisprudence. It had been the habit of publicists, ante-