I think the answer is picking cotton because that's what people can do on the plantation fields and I also learnt about this a little bit in my history class.
It was trench warfare that was used to a great extent in World War I. This led to a significant elongation of the conflict, since targeting soldiers was much harder.
Even if they had, the combined bombers of the UK and US would problably be enough to still win the war, and the fighters would problably take them all down, adding to the Anti Aircraft.
