Most of Crete had been conquered by the Ottoman Empire during the early part of the war against the Republic of Venice and its allies, which was the fifth Ottoman-Venetian War, and began in 1645. The capital of Crete, the fortress of Candia, managed to hold off the Ottomans in their prolonged siege of the city until the last two bloody years, finally resulting in a negotiated surrender on September 27, 1669.
The Venetians lost Cyprus to the Ottomans in the fourth war (1570-1573), making Crete the last major overseas territory of their republic. The Ottomans were expanding their empire and wanted Crete for its strategic location. Although Venice and the Ottomans were technically in a period of peace, the Ottomans were still allied with Barbary pirates. When the Venetian fleet attacked and destroyed a fleet of pirates in the Ottoman port of Valona in 1638, the city was bombed in the process. Sultan Murad IV threatened to execute all Venetians in the empire and cut off all trade, but because of their ongoing war with the Persians, their attention was elsewhere. The Venetians ended up paying the Ottomans 250,000 sequins (zecchinos) as a fine.
On September 28, 1644, the Knights of Malta, a Venetian ally, attacked a convoy on the way to Alexandria from Constantinople. The convoy included Ottoman pilgrims and dignitaries on their way to Mecca, most of which were slain. The survivors, 350 men and 30 women, were kept alive to be sold as slaves. The Maltese took their loot and booty and docked in Crete, which gave the Ottomans reason to accuse them of collusion with the Venetian Republic. Venice denied the allegations and negotiations between the Ottomans and Venetians lasted into 1645. Eventually, the talks fell apart and war was declared. Fourteen years later, nearly to the day, Crete was conquered and the Venetian Republic was greatly diminished in its influence and wealth.