During the Cretan Revolution of 1866-1869, the Ottoman Empire was forced to send several pashas in Crete, but the effort proved fruitless. The latest Pasha sent to the island was Avni Pasha, who faced the continuing resistance of the Cretans and decided to change his operational tactics.
Thus, the measures he took were:
- He provided political protection to those who declared allegiance to the muftis.
- The Turkish fleet ruled the northern coast of Crete, so as to stop supplies coming from Greece.
- Put a price on the Cretan rebels, with 500 ottoman pounds each.
- He settled Kurds and Circassians to the island, in order to strengthen the Muslim population.
- He designed an entire system of large and small towers (called koules) in prominent locations throughout Crete, in order to fully control the island.
Specifically, Crete was divided into five provinces, the governors of which undertook the construction of koules. The koules were built on high hills, crossroads, ports, passages and their guards spied the rebels and the transporting Christians. They intercommunicated (with fanfare or fire) in case of an emergency and delivered the alert message serially to the main camp (called Kiesle). The effectiveness of Koules was devastating for the Cretans, as they could no longer easily intercommunicate.
The Cretans reacted actively during the erection of the towers, harassing the builders, destroying the buildings in the evenings or destroying lime furnaces, from where the Turks supplied lime for building. Nevertheless, Avni Pasha managed to complete his project by using experienced Bulgarian and Armenian craftsmen, who until August 1868 had built more than 60 koules and 2 months later this number increased to 150.
As mentioned, the Turks called these towers koules, after the Turkish kule. The only difference between them and the rest towers of the island is that koules were built by the state, rather than by private feudal lords and onwers (mainly Venetian).
The Cretans, while trying to free themselves, destroyed several Koules, many of which do not currently exist. However, dozens of areas on Crete have relevant place names (koule or pirgos (tower)), that implies the former existence of towers. Due to the large number of the Koules, here we will not deal with all of them, but a few that still exist.
The Turkish forts of Fodele 
Koules of Potami 
Just above the reservoir of the dam Potami still dominates the ruined Koules (Turkish Tower) of Potami, built in the period 1866 to 1869. It has been declared a protected monument, because it is an important sample of castle architecture and is inextricably linked to the history and memories of the area during the Ottoman occupation of Crete in the 19th century.
The mountainous and inhospitable province of Sfakia hosts several small and large koules, ie Ottoman towers, which was built by the Ottomans to control this revolutionary area. One of the most unknown forts lies in ruins in the mountains west of the gorge of Samaria and you can reach it via the trail of the known Koules of Agia Roumeli.
The fort of Koules is located in Paleokastro area, 12km east of Chania, near the village of Kalami and close to the ruins of ancient Aptera. The fort was built by the Turks after the Cretan Revolution of 1866, in the framework of a program to control Crete from a network of towers.
Askyfou Plateau, about 50km south of Chania city, is located in a strategic position and is formed on the passage that connects the southern shores of Sfakia to the north coasts of Crete. Sfakia did always breed great revolutionaries and the Turks always wanted to control them. Thus, in response to the Cretan Revolution of 1866, they began construct Koules, i.e. small castles, in the most important locations of Sfakia.
Here we meet the remnants of a small Koules (Turkish fort) that had visual contact with the koules of Agios Ioannis and Loutro. Almost nothing survives from the fort, apart from some wall foundations. Also, there are modern water cisterns, apparently built with material of the fortress.
Most visitors of Loutro know about the fortress of Koules, which even today dominates over the village.However, they are unaware of the existence of a second fortress which is very easily accessible. The fortress of Kastella is located south of the village and next to the harbor where the big ships from Chora Sfakion stop.
Besides the two Koules of Askyfou, several other Koules had been constructed in the present province of Sfakia in order to suppress the revolutions of the Sfakians.
On the west side of the exit of Samaria Gorge, above the current village of Agia Roumeli, the Turks built the Koules of Agia Roumeli to suppress the rebels hiding in the gorge. This Koules is in quite good condition. There were three more towers in wider area of Agia Roumeli (in Skoteini, Aggelokambos and Sideris positions)
