As economic and demographic methods were applied to the study of history, the trend was increasingly to see the late Middle Ages as a period of recession and crisis. Belgian historian Henri Pirenne continued the subdivision of Early, High, and Late Middle Ages in the years around World War I. Yet it was his Dutch colleague, Johan Huizinga, who was primarily responsible for popularising the pessimistic view of the Late Middle Ages, with his book The Autumn of the Middle Ages (1919). To Huizinga, whose research focused on France and the Low Countries rather than Italy, despair and decline were the main themes, not rebirth.
What wasn't the nationality of historian Henri Pirenne?