Armistice Day in 1918 was arguably the most joyous day of the 20th century. As the guns fell silent, crowds celebrated across the Western world. The foremost artists of all nations including Pierre Bonnard in Paris and Gilbert Beal in New York, were inspired to convey the emotions of the historic moment. The Irish painter William Orpen was in Amiens. The tense and difficult process of making the peace ensued. Orpen and Augustus John...