Defensive system set up by Germans in October 1943, from the Tyrrhenian side of the current province of Massa-Carrara to the Adriatic side in the province of Pesaro and Urbino. It covered a front of over 300 kilometres that ran along the Tuscan-Emilian Apennine reliefs. This defensive preparation was the scene of heavy fighting between the German troops, under the command of Albert Kesselring, and the Allied forces, under the command of Harold Alexander: the first tried to slow down the advance of the latter, who, after having overcome the Gustav Line, tried to open their way towards the Po valley and therefore towards the regions of northern Italy.
The definitive breakthrough of the line occurred in the spring of 1945 when the Allied armies and partisan formations poured into the Po Valley.