By the Schengen Agreement signed on 14 June 1985, Belgium, France, Germany, Luxembourg and the Netherlands agreed that they would gradually remove their common frontier controls and introduce freedom of movement for all individuals who were nationals of the signatory Member States, other Member States or third countries. The Agreement and the Convention, together with the declarations and decisions adopted by the Schengen Executive Committee, make up what is known as the Schengen acquis. When the Treaty of Amsterdam (1997) was being drafted, it was decided to incorporate this acquis into the European Union from 1 May 1999 onwards, since it relates to one of the main objectives of the single market, i.e. the free movement of persons.