Bu effaith y rhyfel yn enfawr. Roedd yna recriwtio torfol, symudiadau a hyfforddiant i ddynion a merched drwy'r wlad. Cafodd diwydiannau eu haddasu neu eu hehangu, a bu newidiadau mewn amaethyddiaeth a choedwigaeth a gafodd effaith ddofn ar batrwm y tirwedd trefol a gwledig ledled Cymru.
The impact of the war was huge. There was mass recruitment, mobilisation and training of men and women across the country. Industries were adapted or expanded, and changes took place in agriculture and forestry, which profoundly affected the fabric of the urban and rural landscape across Wales.