The Florentines formed a commune in his successors' place. The signoria was chosen by the gonfaloniere titular ruler of the city , who was elected every two months by Florentine guild members. During the Republic's history, Florence was an important cultural, economic, political and artistic force in Europe. Its coin, the florin , was the dominant trade coin of Western Europe for large scale transactions and became widely imitated throughout the continent.
The republic had a checkered history of coups and countercoups against various factions. The Medici faction gained governance of the city in under Cosimo de' Medici. The Medici kept control of Florence until Giovanni de' Medici, who later became Pope Leo X , reconquered the republic in Florence repudiated Medici authority for a second time in , during the War of the League of Cognac. The Medici reassumed their rule in after an month siege of the city, aided by Emperor Charles V. The second duke, Cosimo I , established a strong Florentine navy and expanded his territory, conquering Siena.
In , the pope declared Cosimo the first grand duke of Tuscany. The Medici ruled the Grand Duchy of Tuscany until Since AD, the city had been part of the Marquisate of Tuscany. After Margravine Matilda of Tuscany died in , the city did not submit readily to her successor, Rabodo r.
The first official mention of the Florentine republic was in , when several cities around Tuscany formed a league against the then-margrave of Tuscany, Duke Henry X of Bavaria. The country was nominally part of the Holy Roman Empire. The newly independent Florence prospered in the 12th century through extensive trade with foreign countries. This, in turn, provided a platform for the demographic growth of the city, which mirrored the rate of construction of churches and palazzi.
This prosperity was shattered when Emperor Frederick I Barbarossa invaded the Italian peninsula in As a result, the margraves of Tuscany reacquired Florence and its townlands. Florence's population continued to grow into the 13th century, reaching 30, inhabitants. As has been said, the extra inhabitants supported the city's trade and vice versa.
