 Complete the following phrase:  Throughout its involvement in the fighting on the Western Front, the 4th Battalion took part in the following battles: Ypres 1915 Passchendaele 1917; Gravenstafel; St. Julien; Festubert 1915; Mount Sorrel; Somme 1916; Flers-Courcelette; Ancre Heights; Arras 1917; 