There were many reasons why young men joined up, including for a job and money, escaping poverty, patriotism, government recruitment posters, peer pressure, chance to travel, and chance to have an adventure.
The Scottish general Douglas Haig, Commander of the British forces during the war, has been heavily criticised for persisting with this tactic when it was so expensive in human life.
The Battle of Loos was famous for the involvement of Scots soldiers, including the use of gas against British soldiers for the first time, with five Scots awarded top medals for their bravery, and very high numbers of Scottish deaths.
The Battle of the Somme saw the British decide to launch a massive attack on the Germans at the River Somme, to relieve the terrible pressure on the French at Verdun.
The plan for the Battle of the Somme involved bombing the Germans with artillery for 7 days and 7 nights, using spotter planes to accurately target attacks on the Germans, and shelling to destroy the German barbed wire and trenches.
After the numbers volunteering to fight started to drop, the Government introduced a law that meant all British men aged 18 - 40 were to join the army.