The phenomenon most likely to provide the Turks with a casus belli that would justify their invading Crete was Christian piracy, at that time a flourishing business. The Knights Hospitallers of St. John were a military order founded in the Holy Land at the time of the early crusades. When it was finally clear that further attempts to conquer the Holy Land for Christianity would be fruitless, the Knights in their wisdom defined piracy as a continuation of the holy struggle against Islamic power.
The Venetian governor soon showed up and ordered the pirates off, and after a few fruitless attempts to land elsewhere in Crete, they abandoned the galleon and its passengers—presumably in Crete, though the account doesn’t say—and went home to Malta. Another source says that the pirates had killed some of the eminent captives, including the immensely rich chief eunuch of the Sultan’s harem, whose immense riches they divvied up. It seems doubtful that this official would have been carrying his entire fortune with him on the voyage, but as a rich and important Muslim he might have carried a large sum for making charitable offerings, a traditional act of piety for wealthy Muslims on the hajj. This story, at least in part, may be another that sprang up in the hothouse ambience of war fever.
In the spring of 1645 an enormous expedition was organized under the command of the chief admiral, Yusuf Pasha, a warhawk and ally of Jinji Hodja. (Yusuf Pasha’s original name was Josef Masković; he was a Dalmatian convert to Islam.) The Turks encouraged the Venetians to believe that they intended to attack Malta. When the fleet left Istanbul, at the end of April, 1645, it even sailed some distance out of its course to maintain this illusion, successfully keeping the Venetians off their guard.
In spite of the massive fortifications built in Crete during the previous century, the island was in no shape to fend off a full-scale invasion. Its fortresses hadn’t been properly maintained, garrisoned, or supplied, and its landowners had been lackadaisical about their obligation to supply and support a militia. It was a seriously bad moment for the Cretan colony when the Turkish fleet turned in their direction on June 21 and arrived on the northwest coast near Canea (Chaniá) four days later.
The Rough Guide tells of a defense that cost 40,000 Turkish lives, and also cost Yusuf Pasha his head when he took that news to the Sultan, but I can’t find this information confirmed elsewhere. Other accounts say that the Turks granted the city, its residents, and its defenders generous terms in the hope that this might lessen resistance in other parts of the island. That doesn’t sound like something they’d do for people who had just slain 40,000 of their comrades. As for Yusuf Pasha’s unhappy end, it has been attributed to the Sultan’s rage when a Venetian fleet succeeded in blockading the Dardanelles, temporarily preventing the departure of Ottoman reinforcements. Or else it's attributed simply to the perils of Ottoman politics at the time.
The combined fleet arrived at last, too late to prevent the capture of Canea. Its commanders made a couple of attempts by land and sea to retake the city, but these were frustrated. Venice’s allies poked about for a while and then went home; they had never been enthusiastic about the mission. Waiting for them had done the defense more harm than good.
The Turks began taking smaller Venetian strongholds scattered about the island, one at a time. In the autumn of 1646, more than a year after the fall of Canea, they succeeded in taking the next largest city, Retimo (Réthymno), despite its huge Fortezza. The city, which lay outside the walls, surrendered on October 20, and the fortress, which had little left to protect, only three weeks later. The reduction of smaller forts continued until the whole island, except for its strongly fortified capital, Candia, was in Turkish hands.
The siege of Candia itself began in May, 1648. It ended when the Venetian Captain-General, Francesco Morosini, surrendered the keys of the city to the Grand Vizier Ahmed Küprülü in September, 1669—21 years later. (It has been nominated for the honor of being the longest siege in history.)
Sultan Ibrahim didn’t live to see the end of the siege; in fact, it was only in its fourth month when he was strangled at the behest of his Grand Vizier. Ibrahim’s rule had become increasingly bizarre. Besotted with heavy women, he had sent agents throughout the empire to recruit them for his harem. In Georgia they found a woman who weighed 330 pounds and was called by the pet name Şeker Pâre (‘Sugar Lump,’ more or less). She pleased the sultan so well that he awarded her a state pension and the title of Governor General of Damascus. He had also been seen feeding gold coins to the fish in the palace pool. It was obvious that he had to go. (All of this must be true; I found it in Wikipedia.)
During the last two or three years of the siege, attrition gave way to what one historian describes as “a frenzy of destruction and bloodletting.” The illustration above, printed on a map published by Nikolaes Visscher of Amsterdam, may be based on a painting from this period. When a French expedition that represented the last possible attempt to relieve the siege failed and departed, Captain-General Francesco Morosini decided that surrender was preferable to slaughter, the only alternative that was realistically foreseeable. The Grand Vizier refused to budge on his demand for the complete surrender of the island, but his terms were otherwise generous. All Venetians, military and civilian (and also upper-class Greek families who had been integrated into Venetian society) were allowed to depart unharmed with as much of their property as they could carry. Venice was allowed to keep three offshore bases, all on small islands: Spinalonga, off Áyios Nikólaos (which is between Candia and Sitía); Souda, a little east of Chaniá; and Gramvoúsa, at the extreme northwest of the island, near the tip of a peninsula with the same name. All had harbors where Venetian merchant ships trading with the East could take shelter, and for several decades Venice also cherished hopes that they might be instrumental in a reconquest of the island. But such hopes were in vain, and in 1715 these three bases were lost along with all Venice’s remaining possessions south and east of the Adriatic. (The Serenissima Republica itself perished less than a century later when, after being occupied by Napoleon, its territory was divided between France and Austria in a 1796 peace treaty.)
From that time on on Turkish military power was unmistakably declining in comparison to that of major European states. One possible cause was increasing religious and political conservatism in Ottoman society, related to the growth of a network of interest groups inclined to dispute issues of wealth and power with the sultanate. This kind of disharmony tended to impede the empire’s previous willingness to learn and adopt new military techniques and technologies. And as the West went on expanding its oceanic trade—and, through colonization, exploiting the resources not only of the Far East but also of the newly discovered Americas—the Ottomans, like the Venetians, fell behind most of Europe economically as well as militarily.
So, although the Turks might win military victories against rebels inside their empire, or against the infant kingdoms some of these rebels managed to set up during the 19th century, the great powers were certain to intervene in the peacemaking process and force the Ottomans to give back all or most of what they had gained. The common characterization of the empire at that time as the “sick man of Europe” was not altogether false, but at least some part of the illness was probably owing to the treatments of Europe’s doctors.