The first seventy years of the fourteenth century saw continued political strife within San Miniato for control of the commune.
At the same time Florence was increasing its pressure on all the communes in the Val d’Arno to accept its over-lordship and particularly on San Miniato, standing as it did across the city’s route to the sea. In spite of continuing resistance by the Sanminiatese, by 1347, San Miniato had fallen under Florentine rule and in 1364 a chomesaro (commissioner) was appointed to govern the town, although the rocca (fortress) remained firmly in Sanminiatese hands.
Three years later, in 1367, the Saminiatese rose against their Florentine masters and, led by members of the new magnate class including ser Filippo di Lazzaro or Lazzerino and ser Bartolomeo di ser Francesco, briefly re-established their independence. Florence was always nervous of the territorial ambitions of Milan and could not allow San Miniato to remain independent as a threat to its security. Almost inevitably, in 1369-70 the town was besieged and captured by the Florentine militia. A new governing regime was installed and in spite of subsequent rebellions, in 1389, in the mid-1390s and in 1432, San Miniato was firmly under Florentine control.