This stronghold, built because Louis XVI of France wanted to make Brest impregnable, was the most important link in the defense of the city's west side, designed for 500-600 soldiers.

This fort was used by the Germans in 1944, who installed a parachute battalion during the siege of Brest by the Americans.

In 1984 Fort Montbarey was developed by the Navy into a museum on the history of Finistère during the Second World War, featuring the Resistance effort.

An exhibition on "Brest in ruins" is also presented, as well as a "wagon of death" used in the Holocaust[citation needed] and many American vehicles and parts from the DCA (Defence Against Aviation) era, and a British Churchill tank.

The museum also manages over 10,000 files and documents on the Resistance, and records on soldiers and victims of the Second World War.