Iraqi soldiers flea to Europe, page-70

They really had no choice. Charge out of the trench or be shot by your commanding officer.
If say a group of soldiers managed to overpower a commanding officer, where would they go what could they do.
The hangmans noose would await them if they got back home. Their chances of slipping into the surrounding countries as civilians like Turkey also a slim chance of that. They weren't there to fight, they were there to die.
But what would you expect from the imperial colonizing war machine that was Great Britton. They were the best at it and very ruthless.