During the period of Byzantine Empire, various nations wanted to occupy its territories. Trying to organize the defence, the Byzantine cities were the basis of the political, military and ecclesiastical administration and for that reason, their fortification was a major goal of the imperial administration.
 
According to the work of Procopius “Peri Ktismatwn” About buildings, Justinian trying to strengthen the defence of the state, he granted money in order to rebuild the walls of many under ordinate towns, and in order to create or strengthen with fortifications the strategic places of special importance. At the same time, he organized a network of new fortified cities in vital places in order to ensure the protection of the streets and the trade routes.  The fortification practice was not unknown in the ancient world, however in the Byzantine era, it was developed a lot, with many and impressive examples in the whole empire. Fortified cities, citadels, castles, towers, intermediate walls, were created for the defense of the state and ensured the protection the residents.

Although the emperor and the supreme dignitaries emphasized mainly on the diplomacy for the confrontation of the hostile disposals of the neighbors, the organization of the army and navy became an urgent requirement. The organization of the army was based on two corps: limitanei and comitanses. Limitanei were farmers lived in the borders, to which the state granted cultivable ground with the obligation to offer military services. Comitanses were the regular army, under the leadership of the the emperor, who could be transported wherever it was required. Other corps were the allies, the bucellarii and the confederates, that consisted of foreigner condotieres.

However, the Byzantine army, despite the well organization, it could not be a ready for war and effective as a mass, capable of ensuring the integrity of the territories of the Byzantine empire and the safety of the residents, if they were not equipped with the right  military equipment (armor and helmet) and arms. The polemic arms are distinguished between those of fighting hand to hand (sword, lance, club, axe, arcs and arrows) that were used for fighting body to body, and of ballistic arms that struck the enemy from distance. Of this last type were the wall fighting arms, meaning all those which were used during the sieges of castles, such as the battering ram, the pelting, and the tortoise (chelone).  Apart from the army of land, the navy was particularly organized too in Byzantium, as an organic department of the administration of themata (provinces).So, the fleet of the provinces was created, the thematic ploima (watercrafts of provinces), with head generals or drungaries. The Royal water craft was an independent fleet for the defense of the capital with head the drungarios , that had the role of the general admiral.

The Byzantine navy allocated dromons, dromonia and chelandia that were boats equipped, on one hand, with wooden castles “xylokastra”, from where the warriors could throw missiles against the hostile boats, and on the other hand, with throwing machines for “sifones”, the earthen or metal containers that contained the Greek fire. Greek fire was the most perfected version of between now and then known incendiary materials on martial purposes. The main success of it, at the naval battles, was that it caused the confusion and the panic in any hostile fleet, which was forced to leave because of the fire and the bad effect on the moral of the crew of the wooden ships.