QUOTE (truthergw @ Oct 9 2009, 10:24 AM)

Very briefly, a trench to the rear or on a flank which was not connected to the main front line. The trenches at Roeux, south of Arras are an excellent example where staggered trenches and fortified redoubts were staggered back for several kilometres behind the front line.
I agree Tom. Just one point though, Roeux is directly to the east of Arras, not south.