Napoleon once called the port of Den Helder the "Gibraltar of the North". For some centuries the port has been an important naval base. To protect it Napoleon ordered the construction of several forts around the port, including Fort Lassale. The construction of Lassale started in 1811 and had to get five bastions and a number of courtines. It was hardly finished when in December 1813 the Dutch started the liberation of the port. However the French troops under vice-admiral Ver Huell, strangely enough also a Dutchmen. The French only withdrew in May 1814, a month after the conquest of Paris.

After the liberation the Dutch finished the fort and added several building. The most important modification was the construction of the sea front. The two bastions of the northwestern front were incorporated in a new front which also received a 220 m. long bombproof building housing about 1.000 men. On top were several open positions for 24 cm coastal guns. The two white building on the right are part of a German WW II anti-aircraft battery armed with four 10,5 cm naval guns. Nowadays Erfprins is still occupied by the navy which uses it as its main training base.