Sentence:  These qualities endeared him to both the musicians and the social economic haute monde which supported the concert world of the post <WSD>World</WSD> War 1 , era . 
Meaning of the word marked with <WSD> tags:  a war between the allies (Russia, France, British Empire, Italy, United States, Japan, Rumania, Serbia, Belgium, Greece, Portugal, Montenegro) and the Central Powers (Germany, Austria-Hungary, Turkey, Bulgaria) from 1914 to 1918