August 4th 2014 marks 100 years since the outbreak of World War One. Millions of soldiers from Wales and the rest of the UK enlisted to fight in the conflict, which lasted for four years between 1914 and 1918.
Jonathan Hill has been at Mametz Wood, finding out about what happened there and investigating the stories of some of the men who gave their lives.
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.