Short answers, pulled from the story.
Johan Huizinga (the 7th of December 1872 - the 1st of February 1945) was a Dutch historian and one of the founders of modern cultural history. He is best known for The Autumn of the Middle Ages (1919) and Homo Ludens (1938), in which he argued that play is the primary formative element in human culture.
Huizinga's most famous work is The Autumn of the Middle Ages, first published in Dutch in 1919 as Herfsttij der Middeleeuwen. It was translated into German in 1924 and into English the same year as The Waning of the Middle Ages; a new English translation by Diane Webb appeared in 2020 as Autumntide of the Middle Ages.
In 1942, Huizinga spoke critically of the German occupiers of the Netherlands. The Nazis detained him between August and October 1942, and after his release he was banned from returning to Leiden University. He spent his final years at the house of his colleague Rudolph Cleveringa in De Steeg, Gelderland, where he died on the 1st of February 1945, weeks before Nazi rule ended.
In Homo Ludens (1938), Huizinga argued that play is the primary formative element in human culture. He proposed that games, rituals, and ceremonies are not ornaments on social structures but the medium through which those structures are built. An English translation was published in 1955.
Huizinga became Professor of General and Dutch History at Groningen University in 1905. In 1915, he was appointed Professor of General History at Leiden University, a post he held until 1942, when the Nazi authorities banned him from returning to Leiden.
The Huizinga Lecture, or Huizingalezing, is a prestigious annual lecture in the Netherlands held in honor of Johan Huizinga. It covers subjects in the domains of cultural history or philosophy.