The city history begins in 316-315 BC, when king Kassandros united 26 smaller cities and founded this new city-nation, naming it Thessaloniki, after his wife and sister of Alexander the Great. The geographical location that Kassandros chose to found Thessaloniki was no accident. The rivers of Northern Greece disembogued in the Thermaikos Gulf and that was a sufficient and important factor for the communication with the inner grounds. Apart from that, the unique location of the port and its size which was more than adequate to serve the communication with the Black Sea, all of the Eastern Ports and the islands of the Aegean Open Sea, led Kassandros to his decision. Thessaloniki soon became trading center and developed an important naval force.
The democracy regime consists of a Congress and a Parliament, but it seems that the city is basically ruled by a monarch. The Congress and Parliament decisions are taken into consideration, but the final call is made by the monarch whose word written or verbal is equal to law. During the 2nd century BC, just after the battle in Pydna, in 168 BC (where the last Macedonian king, Perseus was defeated by the Romans) the House of the Macedonians is replaced by the Roman Empire and Emilius Pavlos. The cities Veria and Pella became Roman colonies. Nevertheless, the new Monarchs will provide significant help to the flourishment of the city. Greek language remains the main in use and there are only a few inscriptions in Latin. Great monuments are built which are of significant cultural and architectural interest, pre-serving the Greek idea and form. Round the 3rd century AC, the known Roman peace which gave such a huge boost to the city stops existing, there are war incidents concerning the neighbors on the north and east and contradiction among the citizens on policy matters which should be followed. In order to boost the morality of people the Romans decide to honor the citizens giving away titles. In this tensed atmosphere Goths and Herules attack. As far as religion is concerned, inscriptions and coins show that during the Hellenistic and Roman Ages the most common god worshiped was Dionysos. But there were also worshiped a number of foreign gods and goddesses, mainly Aegyptians such as Isis and Osiris, as well as gods from other corners of the world, such as Epona, goddess of Kelts (during the late Roman Ages).In 284 BC, during the times Dioklitianos and Galerios Maximianos Ceasar ruled, the city started being rebuilt. The fortification, built at the same ages the city was founded, complete and adequate to protect the inhabitants, was just partly reconstructed or extended up to the 3rd century AC. In the wider area of Thessaloniki archeologists have recovered five Macedonian single chambered tombs, dated from the 4th- 5th century BC. Unfortunately, there are no significant findings indicatives of the architecture, the painting or the decoration of that era. However, the buildings and the findings we have got from the Hellenistic Ages are numerous and very enlighting as far as the way of life is concerned. The most important public building of those ages is the Agora (the name is in use even nowadays), a place which is known that people gathered and spoke their opinion. The Agora was extending in two different levels which due to the morphology of the ground were climaxing and was in fact a complex of two parallel squares which one followed the other and was surrounded by hallways and the Auditorium. The main entrance was standing at the south side and was decorated by sculptures of gods, some of which are now kept at the Louvre Museum. Excavations have brought to light the entire southeast section of the northern square and the Auditorium. The Auditorium is dated from the 293 – 305 AC and very well preserved are the white marble stones on the floor and the arched hallways.
Rotonda, the Galerius Arch (or Kamara), the Oktagonus and the Horseracing area were all parts of Galerius’ palace complex, as well as commanding base and center of the cultural and religious life of the city. This complex was built in 296- 297 after the victory against the Persians. Worth to mention are the spa facilities and the highly developed system that they worked which due to the fact that the modern city is built on the Roman and Byzantine buildings cannot be brought to light entirely. The wealth of the inhabitants can be concluded from findings of residences which had marble or mosaic floors with geometrical or mythological themes. The most shining era for the city are the ages of the Byzantine Empire, during which Thessaloniki was the cultural and religious center of the Empire. The significant geographical location which casted the city link between East and West was highly pointed particularly when capital of the Empire became Constantinople. Du-ring the ages that Dioklitianos ruled (284- 305 AC) Thessaloniki was the capital of command of the Eastern Illyric block and during the 4th century AC was the second most significant city among the European colonies that belonged to the Eastern Roman Nation, after Constantinople. The pressure of the barbaric races to penetrate the Emos peninsula and their gradual immigration to the outskirts of the Empire grounds constantly indicated the significant part the city had on the commanding control of the peninsula. Galerius Ceasar (who ruled during 293- 311 AC) was the first one who had foreseen and had fully comprehended the gravity of this fact and the chance of control over the barbaric races in the territory he was ruling. The foundation of Constantinople not only did not neutralize the strategic point of Thessaloniki, but moreover enhanced it, being recognized as the commanding center of the entire Illyric space. As far as religion is concerned, after the 4th world religious congress, the Father Bishop of Thessaloniki was placed in chain of command under the five Fathers of church. This is another proof of the radiant influence the city had in the political and the religious life of the Empire. The intrusions of the barbaric races during the 5th century AC did not cause any severe damages or changes on the structure of the city which had as protector and aider Saint Dimitrios (even nowadays Saint Dimitrios is thought to be the protector of the citizens by the Orthodoxs). The solid fortification also was a reassuring measure against every war attempt. In times of barbaric attacks even the inhabitants of the areas around found sanctuary inside the walls. Ioustinianos (527- 565) was the one who built new walls to obtain a fullest and more sufficient measure against every enemy. During the 6th century AC the appearance of Slavians in the Emos peninsula was not considered a serious threat because of the peaceful character these races had. Besides, these first races were nomads with no great force to claim grounds. However, the combined intrusions organized by Slavians and other barbaric races (such as Avarians who attacked in 616- 618 AC) were far more dangerous. But the city was so well fortified that there was no room for delusions since every attack lacked the knowledge of war tactic against a fully fortified city and none of the intruders had the means to last in a long term beleaguerment. So, at the end, Avarians gave up on Thessaloniki and spread to the wider area of Macedonia, organizing stealing intrusions. When the Arabic races started spreading on the north coastal grounds of Afrika and Syria, the Emos peninsula rised even more in the pyramid of power and command among the known world. In 662 the Emperor Konstas the second, on his way to visit the west, stayed in Thessaloniki for a small period of time and valuated the city problems. Bulgarians had established themselves on the Emos peninsula and on the East section of peninsula the Slavian races were getting organized as time went by. Now the threat was more obvious than ever. Ioustinianos the second (685- 695, 705- 711) made an attempt to neutralize the power of the Slavian races and with no great effort managed to succeed, attacking in specific areas, he took a great number of prisoners and damaged the morality of the Slavian ambition. The success was celebrated by the citizens of Thessaloniki by an ovating parade which gave a clear message of the power od the Empire. The dawn of the 8th century finds the city in a mixture of flourishment and rising dangers. The short period of time (535- 732) that religious life depended on the Vatikan was over and th city found again its place in the Byzantine Empire. The eastern Illyric was now under the commandment of Constantinople and that placed Thessaloniki into a very active position in the political and cultural arena. On the other hand, the Bulgarians continued establishing their presence on the Emos peninsula, making clear their goal to move towards the south. The Arabs developed their naval force, threatening through piracy all the coastal trade centers of the Empire. The beleaguerment of Constantinople in 717 by land and sea proves the combined two- pointed threat that every important coastal city faced. The several defeats of the Byzantine army at the end of the 8th century and the beginning of the 9th by the Bulgarians and their leader Krumus (Byzantine- Bulgarian wars) was a peek to the future developments. The threat was rather concerning the weakening of the armies of those European cities which defined the boundaries of the Empire than Thessaloniki which its fortification still stood solid. The peace that was signed after the wars was a positive act for both parties but didn’t last long. In 860 the Bulgarians signed an alliance with the Franks, protecting themselves from the Byzantines as far as the Bulgarians were concerned, and the Moravians as far as the Franks were concerned. That led to a Byzantine- Moravian alliance in 862. At this time Kyrillos and Methodios, two brothers from Thessaloniki were sent to Moravia, in order to get the Moravians acquainted with the Byzantine culture. They created the Slavian alphabet, translated the Holy Bible in the new written language and many other religious books. The Byzantine diplomats on the other hand, after long pressure, persuaded the leader of the Bulgarians Boris to turn his people to Christianism under the teaching of Kyrillos’ and Methodius’ students. Thessaloniki was now a huge trading center, serving Constantinople to lessen the trading conjuction which had become a burden. At the beginning of the 10th century the trading privileges of the Bulgarians were transferred by royal order to Thessaloniki. That caused the rage of their leader Samuel who found a chance to attack. The Byzantine- Bulgarian war began. The damages were severe. In 996 the Emperor Vasilios Vulgaroktonos (his surname means the one who kills Bulgarians) decided a full attack against the Bulgarians having his military base in Thessaloniki. At the battle in Kledios (1014) Samuel died and that meant victory for the Empire and the end of every conflict. Bulgary was now a part of the Byzantine Empire and therefore no more a threat. During the last decades of the 10th century a new threat came forward, the Normandians. The city was beleaguermented by sea and land (1185) and that caused panic to the citizens. Unready and startled as the military force of the city was, it was taken by the Normandians. Help from Constantinople was late. The city remained under Normandian command for three months during which it was heavily damaged. The citizens suffered great losses and many died horribly. Alexios Vranas was the one who was assigned to take revenge and by November of the same year the city was back to the hands of the Byzantines, once more severely damaged. The beleaguerment of Constantinople by the Crusadors (1204) and the distribution of the grounds included Thessaloniki which was given to Vonifatius Mompheratus and the Franks. Up to 1223 the city was the capital of a local Frank reign. In 1223 Theodoros Agelos Dukas Komninos took over Thessaloniki without resistance, as the citizens considered him a liberator from the social and religious frustration the Franks had caused. Theodoros decided that Thessaloniki would be the center of his nation which extended from the Aegean open sea to Adriatic and he was planning to take back Constantinople, but in 1230 he was captured and tortured by the Bulgarians. In 1261 Constantinople returns to the hands of the Byzantines and the Empire which is ruled by the house of Paleologos begins being reconstructed. The threat of the Normandians was neutralized in 1282 and Thessaloniki was now the political, military and the cultural center of the European section of the Empire. The 14th century was a flourishing era for the city which was very active culturally and was constantly developing. Nikiforos Humnos, Thomas Magistros, Grigorios Palamas are only a few names who helped knowledge and art be resurrected. This outstanding rhythm of development was very clear to the consciousness of the citizens who had great urge to take part in social life and by this urge the movement of Zealots was created. This movement was basically setting the matter of Thessaloniki being an innepended city in the Byzantine Empire. Of course, such a demand was never going to be acceptable by any Emperor and the movement was completely neutralized with the entrance of the Emperor Ioannis Katakuzinos in the city in 1349. The last centuries of the 14th centuries are dominated by the rising Ottomanic threat. In 1387 and after three years of constant battles Thessaloniki is taken by the Ottomans and in 1394 is under the command of Vayazit Sultan. Shortly after, the Ottomans are defeated by the Mogolians and the Ottomans after signing a treaty , return the city to the hands of Emperor Manuel Paleologos the second. But as the threat remained, Manuel turned to the Venetians and ended signing a weird treaty according to which Thessaloniki was commanded by the Venetians (1423). This fact only enhanced the Ottomanic threat.