There is often some debate about just how flexible artillery was during the First World War. The following quote was an eye opener for me, and comes from 'The Battle of Loos' by Philip Warner. It is an account written by Captain Wyllie, Royal Scots Fusiliers (written in 1952).
'Captain Brodie now ordered me to go forward into the front trench system and find out what had happened. I took six men with me and we advanced in extended order at a walk. We were much too tired to go forward at any faster pace.
The top of Fosse 8 was still an efficient German OP and I had no sooner started than a heavy shell fire opened up from the German guns. They were using shrapnel, but the range was just out as the shells were bursting just over our heads while the shrapnel itself went into the ground behind us, doing no harm although making a loud noise. I had about 350 yards to go and lay down twice in this distance for a rest.
As soon as I got up the guns started again, but retained the same error with true German precision. I soon slipped into a communication trench and proceeded cautiously up this. The Huns were watching me as they followed me all along the trench with shrapnel which burst just above us, but doing no harm ....
The Huns were still intent in trying to bag our little force and as soon as my position in the trench permitted, restarted a heavy fire, again with shrapnel - perfectly timed, but once again they drew a blank.'