I am at a complete loss as to how I can go about finding what regiment my Great Gradfather fought in in the First Wolrd War. He was from Ardress in County Armagh or possibly Portadown in County Armagh. His name seems to be unusual for this area - he was James Tennyson (known as Jemmy). According to family folklore he was well decorated in the British Army. I believe he died after the war as a result of the gassing he suffered while serving. There must be some way of accessing records that would give me an insight to his time in the army and I hope someone can point me in the right direction.