For the history:

The fortress in Bizani, Ioannina, is a construction by cooperation of the Turkish and German conquerors.

The Germans offered the know-how they had from concrete constructions to help the Turks to be appropriately fortified by the Greek troops and to remain conquerors of the City of Ioannina.

Part of the fort from above.

The History of the Liberation of the City of Ioannina:

In February 1913 the army’s elite squadron had dismantled outside Ioannina, at Hani Emmin Aga, from where they run the operations in Epirus. Their main concern was in the fortress of Bizani, where 30,000 Turks led by Esat Pasha severely defeated all the attacks of the Greeks. Bizani was a hill south of Ioannina, a natural fort for the Turks, which was impregnable for the Greek army.

The Greek troops in vain tried for four months to overwhelm it. The successor Constantine and the staff were in Hani Emin Aga and were struggling to find a solution to occupy Bizani. For his success was important the role of the Greek spies, who were in the Turkish troops, and the contribution of Nikolay Efendi, who served at the Turkish Staff and provided critical military information on the Greek side. Ultimately, however, the invasion of the fort was made possible by the initiatives of the governors John Velissarios and Giorgos Iatridis, who did not obey the commands of the headquarters and acted voluntarily. For the liberation the Greeks prevailed numerically over the Turks, since they had arrived in Macedonia. The plan, like most successful military ventures, was set up in order for the enemy to be misled. The Greek troops would encircle the fortification of the Turks westward from the extremities, while central and eastern attacks would be fought. At the same time, the Evzones had destroyed the telephone networks by interrupting the fortress’s communication with the city. The movement of the 1st Evzonian Constitution, with Major Velissarius, approaching Giannena in spite of orders, judged the outcome of the battle.

The lack of communication with the fort, led Esat Pasha to believe that Bizani fell while in reality they were still intact. At that time, he instructed to surrender to the Greek army unconditionally. In the early hours of 21 February, the Turkish officers handed over to the successor Constantine, who was in Emine Aga, the city of Ioannina. The Velissarios initiative became a savior for the Greek troops that struggled for months and thousands of lives of Greeks and Turks were saved. His bold act led the successor Constantine to tell him the legendary phrase “either I will biff you or I will kiss you, I prefer to kiss you”. On 21 February 1913, Ioannina was now free after 480 years of slavery. The next month, Georgios I was assassinated and the successor Constantine vowed King of Greece.