He enlisted in the Irish Brigade and fought in the Nine Years' War, before securing employment in the household of Cardinal de Bouillon, the French ambassador to Rome.
[2] In Madrid he became the leading agent of Jacobite activity in Spain, assisting in the affairs of Irish emigres and exiles, such as James Butler, 2nd Duke of Ormonde, and facilitating the entry of men into the Regiment of Hibernia.
In 1705 he also became an informant for the French diplomat, the Marquess of Torcy, to whom Bourke sent detailed written reports twice a year in return for an annual subsidy of 6,000 francs from Louis XIV.
In 1715, the Spanish diplomat Giulio Alberoni commissioned Bourke to conduct an embassy to Charles XII of Sweden, but the mission was later abandoned.
[1] The Spanish refused to reimburse Bourke for the task, despite the capture of his wife and children by the British admiral George Byng while they were sailing to Sweden.