In the aftermath of the collapse of the Marijnen cabinet, Cals became Prime Minister of the Netherlands on 14 April 1965. After two decades of economic growth, his cabinet experienced a slight recession. Plans to build sports halls, roads and houses had to be tempered. In Limburg the coal mines were closed and plans were drawn to educate and re-employ the former miners. There was also social unrest ('the sixties'), which became apparent in the Provo movement, construction worker protests, riots over the marriage of princess Beatrix in Amsterdam and the rise of new parties like Farmers' Party (BP), Pacifist Socialist Party (PSP), Reformed Political League (GPV) and the Democrats 66 (D'66). Especially the last party wanted to change the political order .