20th century. Civil War
Following the dynamics of previous centuries, the hill was again a scene of war. Once the fortification work was completed, the interventions were minimal during the conflict (1936-1939), although they included the installation of anti-aircraft batteries in the bastions of the King and Queen or the use of some areas of the hill for execution by firing squad.
There were also small works, such as the construction of the bomb shelters beneath the Castle of the King or the bunker built in the Louvigny bastion area, both still visible. Finally, the cathedral was converted into a concentration camp as of April 1938.