An explosion taking place on the Somme. According to the existing caption it is a controlled explosion set up by the Royal Engineers, to clear the way for the advance. A uniformed soldier, possibly a member of the Royal Engineers, sits on a wooden post watching the explosion. A retreating army often laid obstacles and sabotaged any equipment or weapons they left behind, in an attempt to hinder any advance. Royal Engineers, as well as taking part in the fighting, were also responsible for ‘combat engineering’; finding solutions to engineering problems on the battlefield.