organised Arranging in french algeria by retired french army generals maurice challe ( former commander-in-chief in french algeria ) , edmond unk ( former inspector general of the french air force ) , UNK zeller ( former chief of staff of the french army ) and raoul salan ( former commander-in-chief in french algeria ) , it took place Process_start from the afternoon of 21 april to 26 april 1961 in the midst of the algerian war Military_operation ( unk ) .