The skills of Welsh miners are put to use digging tunnels under the Western Front battlefields.
At the start of the war, miners were considered too important to send into battle. However, when the Western Front came to a standstill, their skills were needed to help dig tunnels under the battlefields where mines could be placed and exploded to help attacks above ground.
Welsh miners became so valuable that the army took away age and height limits to allow more miners to enlist.
Conditions in the tunnels were dark, dirty and dangerous. The diggers were in constant danger of being discovered by the Germans, who would blow the tunnels up.
About 4,500 miners from South Wales were tunnellers during the war - about 200 of them were killed.
In 1916 Field Marshal Haig commented on the role of the tunnellers:
“Their skill, enterprise and courage have been remarkable”