Peat Bog Soldiers was written in 1933-35 by the first inmates of Dachau Concentration Camp set up by Hitler and the Nazis. Most of the inmates were socialists, communists, trade unionists and those with religious beliefs that Hitler did not agree with. The first camps were not, as with later ones, set up as camps where death happened on arrival, they were forced labour camps, as can be seen from the slogan above the entrance gate . Many inmates died from malnutrition, beatings, summary executions etc. The song tells of the labour where inmates were driven to the moor to dig in the most brutal and harsh conditions. The last verse & chorus contains hope for the future.

Any IWW (Wobbly) song written by Joe Hill was written before 1915 when Joe was legally murdered.   

Woodie wrote may in the Thirties... If You Ain't got the Doh Ray Me etc and most famously "This Land is Your Land" written in reply to the Nationalistic slant in Irving Berlin's 'God Bless America'. But you have got to get hold of all 6 verses not just the three that are deemed politically correct by the right wing American Establishment.

Often soldiers who were placed in the most difficult situations by their political masters & generals wrote songs, usually to well known tunes of the day. There are many from WW1. My personal favourite is a full version of D Day Dodgers from WW2,