Since the Middle Ages the defence of the Versilia coast where now the towns of Pietrasanta, Forte dei Marmi and Seravezza lie, was a priority for the governments of Lucca, Pisa and Florence alike, intent as they were in developing their commerce by land and by sea.
Under the control of the Medici family first and the Lorena later, the coastal area developed rapidly with the construction of a road network and towns as well as drainage works and the fortification of its ports. Pietro Leopoldo carried out a social and economic reform of his State after the long period of stagnation under the last Medicis.
The Grand Duke personally visited the Versilia region several times and recognised that it was necessary to build a fort precisely where today Forte dei Marmi stands, between the tower of Cinquale and that of Motrone.
In 1785 the Grand Duke wrote that the fort should "defend the coast as well as provide barracks for the soldiers". Construction work began and in 1788 the fort had its first keeper, lieutenant Niccola Leonetti. In 1794 the soldiers stationed there had to ward off an enemy ship passing in front of the marble wharfs.