Cézembre has been occupied for centuries. Located just 14 kilometers from Saint-Malo, the island has played host to hermits since the 12th-century. Subsequently, a monastery and several churches were built on Cézembre. Towards the end of the 17th-century, the island was fortified by Sébastien Le Prestre de Vauban and maintained a military-type function until the end of World War II. 

On August 6, 1944, the allied forces begin to bomb Cezembre after capturing St. Malo. Stationed on the island was a garrison of about 300 German and Italian soldiers who refused to surrender. It would become known as the most bombed location of WWII between August and September 1944 as the garrison held out. However, they eventually surrendered.