Complex sentence: The remainder of August, all of September and the beginning of October were relatively quiet, with Canadian efforts devoted mainly to preparations for another offensive, although none took place, largely because the British First Army lacked sufficient resources for the task.
Split into simpler sentences: The remainder of August, all of September and the beginning of October were relatively quiet, with Canadian efforts devoted mainly to preparations for another offensive. No further offensives took place however, largely because the British First Army lacked sufficient resources for the task.