Land and Freedom is a film from 1995 by Ken Loach. It narrates the life of an unemployed worker and member of the Communist Party of Great Britain. He decides to leave Liverpool and go fight for the republican side in Spain, during the civil war. The film went on to win several awards.
It draws strong comparisons to George Orwell's Homage to Catalonia, who was also a volunteer for the same side in the war, as well as Ernest Hemingway.
It's an extremely engaging film, looking at the political differences between the Soviet-backed forces and the anarchist forces -- the POUM. David, the main character, initially went to fight for the former, but coincidentally fought for the latter (of which he hadn't heard about) -- either way, fundamentally he wanted to fight against the fascists so he could be doing something he believed in -- his socialists beliefs -- and prevent the spread of fascism to the rest of Europe.
He ends up getting confused about the 2 different sides, who're meant to be fighting for the same thing, yet at the time, not really realising the dangers of Stalinism and the Soviet-backed forces, despite them having access to reliable arms, etc. There is an extremely compelling scene in the film between the POUM members discussing whether or not to collectivise land, what is the revolution about, and again Loach goes a step further than just showing a fight against the fascists but a social revolution in the making. This really shows the differences between real communism and Stalinism and thus the film also serves as an educational resource. My favourite film by Loach thus far.
You can watch the whole film, legally, on YouTube: