• 1815: First commercial exploitation as a gypsum quarry. • 19411944: During
World War II, the
German occupiers converted some of these tunnels for industrial use. The SKF
ball bearing factory was moved there from south of Paris. At the time of the
Allied invasion, the manufacture of ball bearings had been started. The two main tunnels were connected and an entrance structure with gates was constructed. Before their evacuation of Paris, the
Germans destroyed the equipment in the tunnels. Several places in the area of the plant show evidence of fire. According to a villager, the Germans used oil fires to destroy the equipment. This caused cracking and falling rocks. Mines and booby traps were left behind in the tunnels and the nearby woods; these were removed, along with the remains of the plant, by the
U.S. Army. There is no evidence that the Allies bombed the tunnels during the occupation. • 1946: The French Air Force used the quarry as a depot. • 1957: The creation of the Air Defense Operations Center (''Centre d'Opération de la Défense Aérienne'' - CODA). • 1961: The creation of the Territorial Air Defense Staff (
Etat-major de la Defense Aérienne du Territoire - DAT) and the Air Force Air Defense Command (
Commandement Air des Forces de Défense Aérienne - CAFDA). These organizations were dissolved in 1994 and replaced with the Air Defense and Air Operations Command (
Commandement de la Défense Aérienne et des Opérations Aériennes - CDAOA) and its Air Operations Center (
Centre de Conduite des Opérations Aériennes - CCOA). • 1963: Creation of BA921, attached to the 2nd Air Region, and the installation on the surface of the
Strategic Air Forces Command (
Commandement des Forces Aériennes Stratégiques - CFAS). • 1967: Installation of the Strategic Forces Operations Center (''Centre d'Opérations des forces stratégiques'' - COFAS) underground. • 1988: BA921 takes the name "Frères Mahé" ("Brothers Mahé" in English) in homage to three brothers killed in the command of their aircraft. • 1992: Installation of the Special Operations Command (
Commandement des Opérations Spéciales - COS). • 2000: BA921 was attached to the Northern Air Region. • 2006: Special Operations Command (COS) moves to BA107 at
Villacoublay. • 2007: The Air Operations Center moves to BA942 at Lyon Mont-Verdun. At the same time, the Air Defense and Air Operations (CDAOA) moves to BA117 in Paris and the Air Information Center (
Centre de Renseignement Air - CRA) moves to BA128 at
Metz. • 2011: BA 921 is disestablished on 5 July 2011. • 2020 : In the spring of 2020, it is decided to relocate the headquarters of the Strategic Air Forces on the base, i.e. a hundred people plus the ancillary services in 2024 == Nuclear deterrent ==