In the bitter sixteenth-century conflict between the Spanish and Ottoman empires, both sides relied on espionage. For Jewish men like Simon Sacerdoti (c.1540-1600), whose home had fallen to Spain, expulsion by King Philip II (1527 – 1598) was a very real risk. But Sacerdoti, scion to one of Milan’s wealthiest Jewish families, had direct access to high-level information from the enemy Ottomans, information that was of great value to Philipp and to Spain. Sacerdoti, thus, found himself serving a king and an empire with a long history of harming the Jews, while spying on the Ottomans, a far more tolerant power. This talk explores Sacerdoti’s actions and motivations and shines new light on early modern diplomacy and espionage, and on the place of the Jews in a time of competing empires and loyalties.