In the beginning of the 4th Century AD, Florence became the seat of a bishopric. The city passed under Byzantine and Ostrogothic rule successively and expanded throughout these periods, even though it was often pillaged and laid under siege. At various times Florence’s population dropped to 1,000 inhabitants. Around AD 500, the city was brought under Lombard rule, and peace was restored. However, in AD 774, the King of the Franks, Charles the Great, conquered Florence and it became part of the Tuscany province, the capital of which was Lucca. Trade gradually grew and the city’s population began to rise again, and Florence and Fiesola became a united county in AD 854.

In about AD 1000, margrave Hugo, of Tuscany, established a residence in Florence, instead of the capital Lucca, which prompted Florence’s ‘Golden Age’ of art. As a result, construction of the Basilica di San Miniato al Monte commenced in 1013. Between 1059 and 1128, the façade of the baptistery was redesigned in Romanesque style.

After 1115, Florence was governed by an autonomous community, but was marred by internal strife in the 13th Century, as conflicts erupted between the Guelphs, who supported the Pope, and the Ghibellines, who took the side of the German emperor. Eventually, the Guelphs triumphed, and afterwards they split into the Black Guelphs and White Guelphs, who started fighting among themselves, with the White faction finally being exiled. Among the White Guelphs was the famous Italian poet Dante Alighieri. Dino Compagni, an Italian historical writer, and supporter of the Guelphs, wrote about this turmoil in his Chronicles of Florence.
 
Political conflict notwithstanding, Florence continued to enjoy economic progress and became one of the most powerful cities in Europe, assisted by its own gold currency, the florin, introduced in 1252. Florence’s main economic rival was Pisa, which was conquered by Genoa in 1284, and by Florence itself in 1406.

The late 13th Century witnessed the emergence of an anti-aristocratic movement, which resulted in a set of statutes called the ‘Ordinances of Justices’, adopted in 1295. These laws were directed against influential aristocratic clans and supporters of the said Ghibellines, identified by name within the statutes. Their members were not permitted to hold office, and doubled punishments were reserved for crimes perpetrated by them. The severity of these statutes was mitigated in later years, although they remained on the books. They actually had the long-term effect of ceding authority over the city to the guilds.