 The Republic of Siena in its progressive territorial growth saw its borders expanding especially in the territories of southern Tuscany in the current province of Grosseto.The possession of an "access to the sea" by Siena was therefore a natural continuation of its expansionary and commercial policy in the Maremma with the conquest of the ports of Talamone, Porto Ercole and Porto Santo Stefano..In order to ensure access to maritime traffic and a competitive sales network, Siena already tried to secure the use of the Grosseto river port in the 13th century.