Communities were shattered and little of the country was left untouched by the horrors of World War One.
But here in Wales, there are three villages where all the men who served in the trenches safely returned home - and they are known as the 'Thankful Villages'.
People across Wales are switching off their lights for an hour this evening and lighting a candle of remembrance.
ITV Wales correspondent Richard Morgan writes about his experience of researching the stories behind those killed in the Great War
All in one place: See some of ITV Wales's reports marking the centenary of the outbreak of the First World War here.