Passchendaele lay on the last ridge east of Ypres , from a railway junction at Roulers , which was an important part of the German 4th Army supply system .

Operation Hush was intended to begin Process_start when the main offensive at Ypres had advanced Cause_to_make_progress to Roulers , Koekelare and Thourout , linked Connect by advances by the French and Belgian armies in between .