Construction of the fort did not begin in earnest until 1801, under Napoleon, in order to protect the coast (and especially the arsenal of Rochefort) from possible incursions by foreign (and especially British) navies. At that time, cannons only had a limited range, and the distance between the two islands of Aix and Oleron was too large to block the passage.


Fort Boyard with gaff rigged sailboat.Following difficulties in establishing a firm base (stone blocks had to be installed on the sandy sea bed during low tide, where they could still sink under their own weight) the project was suspended in 1809. Construction resumed in 1837, under Louis-Philippe, following renewed tensions with the United Kingdom. The fortifications were completed in 1857, with sufficient room for a garrison of 250 men.

However, by the time of its completion, the range of cannons had markedly increased, making the fort unnecessary for national defence.