The Netherlands – from the Dutch for 'Low Countries' – refers to the counties, duchies and principalities around the mouth of the River Rhine on the North Sea coast and corresponds roughly to what are Holland, Belgium, Luxemburg and a small part of northern France. Margaret of Austria, regent of the Netherlands, was younger than Philip the Fair and technically should be shown on the right. Charles, who had grown up in the Netherlands, was compelled to delegate power first to his aunt Margaret again and then to his sister Mary of Hungary from 1531. In 1548, Charles persuaded the Diet of the Holy Roman Empire in the Treaty of Augsburg to recognise the Habsburg Netherlands as a separate and single entity and laid down that it would pass to the emperors’ heirs in perpetuity. The duke of Alva was deeply opposed to Protestantism and determined to take a ruthless approach to the problems in the Netherlands.