The Vestingwet (eng: Fortification Law) or Wet tot regeling en voltooiing van het vestingstelsel (eng: Law to regulate and complete the fortification) was signed on 18 April 1874. The law dealt with the defence of the Netherlands against enemy attacks. The main principle was defence by flooding where as the army of the Netherlands would withdraw to the area around Amsterdam. After the Franco-Prussian War (1870–1871) it became clear that a new defence plan was needed. The law was made by the Minister of War under King Willem III. The Law became dysfunctional at 28 March 1938.