The Women's Land Army (WLA) operated during the First and Second World Wars because so many men were called up to the forces. The women who worked on the land were called Land Girls.
The Board of Agriculture organised the Land Army during the Great War, starting in 1915. Towards the end of 1917 there were over a quarter of a million women working as farm labourers with about twenty thousand as official Land Army women, although it was not, at first, popular with conservative farmers because farm work had always been a man's job.
So by the time the Second World War loomed, there was already some experience of getting women to work on the land. It was easier, therefore, to start the Women's Land Army in June 1939. They didn't just recruit young women from the countryside, but a third came from cities. It began in a voluntary way and ended up with women being called up (conscripted) to get to a total of eighty thousand. It continued until 1949 because it took time to bring men back from overseas and reorganise the workforce.
The effect of the Land Army and the fact that women were also working in factories, changed the nature of work in Britain forever, with many more women going to work after the war. Before the First World War it was uncommon for women to work; after the Second World War it became normal. And the effect was dramatic, for with two people working in each family, families could bring in more money and so buy more goods and improve their standard of living.