Olivier Messiaen
Messiaen wrote a long piece for orchestra called the  Turangalîla  Symphony.  It was first performed in Boston in 1949 with Bernstein conducting.  The French government commissioned a piece called Et exspecto resurrectionem mortuorum (And we expect the rising of the dead) which was dedicated to people who had died in the two world wars.  It was performed in the Sainte-Chapelle in Paris and then in Chartres Cathedral in 1965 in the presence of General Charles de Gaulle.  In 1966 Messiaen became professor of composition at the Paris Conservatoire.