 During World War I, he was head of the British delegation to Mexico, in Mexico City, and was involved in the interception of the German Zimmermann Telegram that was used to promote the entry of the United States into the war.Although acting anonymously at the time, he later identified himself as the mysterious "Mr. H" responsible for intercepting the inflammatory telegram.In 1920, Hohler served as the High Commissioner of the British Legation in Budapest, Hungary.