In 1472, five years after the founding of the Order of Knights of Saint-Michel, King Louis XIth returned to the Mont Saint Michel to leave an iron cage there, in which it pleased him to imprison his political enemies.
With this event, the role of the monastery as "the Bastille of the sea", a fearful prison from which escape was impossible, began.
Until the French Revolution, political prisoners
locked up in the iron cage or in the Abbey's dungeons were mainly pamphleteers and Jansenists.
After the storming of the Bastille in Paris in 1789, marking the beginning of the Revolution, it was the turn of the "Bastille of the sea", first to be occupied in 1790 and then to become a prison for priests who refused to submit to the new Civil Constitution for the Clergy.
Later, under Napoleon the First's Empire, in 1811, it became a major prison through which fifteen thousand prisoners passed and sometimes
died, until it was finally suppressed by Napoleon IIIrd
in 1863.
In those dark years, countless revolutionary
French leaders, such as Barbés, Raspail,
Blanqui, were imprisoned in the dungeons of the
Mont Saint Michel.
In the XIXth Century, Victor Hugo and other Romantic writers were to denounce the use of the Mont Saint Michel Abbey for these purposes, as well as the considerable damage inflicted on the monument during that period.