When the fighting began again it was not trench work.  That was already in the past.  Of course the armies took advantage of whatever shelter was offered them, and there were times when shallow trenches were dug with feverish haste.  But these were only to be used for minutes or for hours, not for weeks and months at a time.  The great battle had become one of open warfare, and it ebbed and flowed over miles of meadow and woodland, of hill and valley.