5921954 Welsh Guards in a reserve trench at Guillemont on the Somme, September 1916 (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: Welsh Guards in a reserve trench at Guillemont on the Somme, September 1916. Photograph, World War One, Western Front, 1916. Trenches were not dug randomly, but were part of a complex design. Each of the front line trenches was backed-up by second and third lines: ?support? and ?reserve? trenches. Communication trenches linked them all together. Soldiers did not spend their whole time in the front line. Whilst one unit was at the front others would be in support in case of attack, or out of the line entirely, resting and training in the rear areas. From a collection of 164 official photographs.); by National Army Museum ; out of copyright.