Which intergovernmental military alliance signed in 1949 are Denmark and the Netherlands both members of? 
Denmark–Netherlands relations:  Both countries are full members of NATO and the European Union. NATO: The North Atlantic Treaty Organization (NATO ; French: "Organisation du Traité de l'Atlantique Nord" ; "OTAN "), also called the North Atlantic Alliance, is an intergovernmental military alliance between several North American and European states based on the North Atlantic Treaty that was signed on 4 April 1949.
NATO