Pretty much every book you read describes how the trenches on the Western Front stretched from the North Sea to Switzerland, but were they all connected? Would it in theory have been possible to walk from north to south without ever coming above ground?
The system as a whole did indeed run the full length, but the theoretical of walking one end to the other in a trench is...not quite there. More can always be said if anyone would like to address the trenches; for the meantime, OP, as the question has come up before, you may be interested in these previous threads: