Unfortunately the initial prosperity of Florence was short lived. The burgeoning population was suddenly stunted by numerous invasions such as Ostrogoths, the Byzantines and the Lombards. When the Roman Empire collapsed in the 5th century it affected its economic life. Trading stopped and was diverted away from Arno Valley and the population slowly dwindled. It was at this time that the construction of the Santa Reparata began.
The devastation that Florence saw under these invasions was repaired when the Franks under Charlemagne took over. They conquered large parts of Italy, where Tuscany was one and slowly the economy revived. In 854 Lothar I consolidated Florence and Resole and made Florence the seat of government that immediately brought with it privilege and prosperity. The population increased, the city expanded to the other side of River Arno, the churches and cathedrals underwent expansion and the first monastery in the city came up.
During this time, merchants, traders, craftsmen, artisans and the middle class flourished. The clergy who were prospering wanted more power and autonomy. Soon a difference of opinion ensued between the Emperor and the Pope about giving Florence self-governance. In 1115 Florence finally acquired autonomy but was officially recognised by the Emperor only in 1183. It was after the death of Henry V in 1125 that the monarchy lost its hold on Florence and self governance took over. In the 12th century however the empire started gaining power again.
In the 12th century Florence established a communal constitution wherein the power lay with the aristocracy and the important members of the merchant classes. The nobility started gaining foothold again. The feudal lords too were stripped of their autonomy, while at the same time there were disputed amongst the nobility as well. The governance was taken over by a professional politician who was in charge of public life. This was a period of political instability.
The various clubs that sprung up were always competing against each other and in an attempt to outdo each other, they all commissioned new buildings to prove the status of the club. There was huge cultural progress and architectural development. The Romanesque style flourished in this period.
The Guilds, one of the most important organisations formed during the 13ht century was a group of artisans and merchants. The guilds controlled trade and commerce and also had political power and also funded artistic projects. The struggle between the papacy and the Empire continued through the Guelphs and the Ghibellines, supporters of the Pope and the Emperor respectively. The Guelphs got the upper hand after the death of Emperor Frederick II in 1250.
Construction and beautification plans came into being. Many squares and street were laid, bridges and cathedrals came up. Work started on the Duomo or Cathedral in 1296.
14th century was a turning point in Florence history. There were a lot of internal and external conflicts, in 1333 huge floods damaged the city, in 1348 there was a sever outbreak of plague that killed thousands and in 1378 the city' poor rebelled and stormed the Palazzo Vecchio and forcefully elected Salvestro de' Medici as the chief magistrate. For a brief period the lower classes ruled the city until the Medici power rose.