Depends on where they were and when. Men fighting at the Russian front faced severe cold in the winter, mud in the summer. Men fighting in the tropics faced heat and torrential rain. Men on the home fronts faced shortages of most things. Your question is simply too broad to answer in a meaningful way.
Neutral
Shocking
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Britain was not invaded in World War 2 and there was no Holocaust in Britain.
Life was hard for Singaporeans and they were tortured.
It was losing until the US joined.
German U-boat attacks
They are dumb so they eat cheese and that made it easy for them.
Deplorable sanitation conditions in the trenches led to outbreaks of disease. Trench Foot was pandemic, and morale was low.