Kaiser is the title historically used by German and Austrian emperors. In German, the title in principle applies to rulers anywhere in the world above the rank of king. In English, the word kaiser is mainly applied to the emperors of the unified German Empire (1871–1918) and the emperors of the Austrian Empire (1804–1918). During the First World War, anti-German sentiment was at its zenith; the term kaiser—especially as applied to Wilhelm II—thus gained considerable negative connotations in English-speaking countries.