Many are familiar with the long and exciting history of the Most Serene Republic of Venice, one of the most powerful Italian states in the history of the Mediterranean, but few know one of the main reasons for the longevity of the Venetian state: the world's first institutionalised secret service. For centuries, the Republic was a commercial and diplomatic power capable of rivaling great European kingdoms as well as its all-time enemy the Ottoman Empire of the Turkish Sultans. One of the tools that enabled the small Venetian state to prevail over these powerful adversaries was an efficient system of intelligence, spies and covert operations aimed at defending the Republic from any external or internal threat.

The Venetian secret service differed from the secret operations of other kingdoms in that it was institutionalised and organised according to pre-established political bodies and institutions. The Council of Ten was the political body in charge of the security of Venice and it was entrusted with the control of Venetian secret agents. The Ten in turn appointed three State Inquisitors who were powerful magistrates, responsible for the conduct and loyalty of Venetian citizens, to nip subversive activities or treason in the bud.

Venetian agents were active at almost all European courts and more active than elsewhere at the court of their bitter enemies, the Ottomans in Istanbul. The infiltration of agents served to control the movements of enemy armies and fleets, as well as to create scandals to damage Venice's enemies or sometimes physically eliminate foreign dignitaries if they were considered a threat. A notable figure in this sphere was Antonio Cappello, Venetian ambassador and secret agent at the court of Spain, who in the 16th century managed to obtain essential information on suspicious movements of the Habsburg fleet. Another famous episode of espionage was the one against the Ottoman fleet before the Battle of Lepanto (1571), the efficiency of the Venetian secret service allowed the fleet of the Italo-Spanish allies to anticipate the movements of the Turkish fleet and prevail.