At the start of this period some industries began to fail and employers cut wages to save costs. Many workers became militant and in Tonypandy there was a strike and a miner was killed by police. Troops were sent in by the Home Secretary, Winston Churchill, though he held them back. The strike ended in 1911 with the defeat of the miners.

During the First World War working life underwent profound changes. The heavy industries of the south expanded. Workers were engaged in the war industries making armaments, and the declining textile industry also made a brief comeback. By contrast other traditional industries were disappearing, for example slate quarrying, as house building ceased because of the war. Women were included in the workforce in large numbers, some in agriculture and others in munitions factories.

After the war, unemployment set in again and many people left Wales to seek work in England. Mechanisation led to a need for fewer workers on the land and rural unemployment also rose. The Second World War eased the employment question but many lives were lost and Swansea was heavily bombed for three nights.

In more recent years new industries: the service sector, administration, chemicals, house and road construction have all contributed substantially to national prosperity.