More than the communist movie people involved. Most of the charecters were played by actual mine workers who had gone on strike and inspired the film. People were playing themselves (approximately). It was written collaboratively in big meetings which included the Hollywood people and the workers.

The union itself was noteable for refusing to bend to the red scare in a context when all the others did. It got blowback from the rest of the labor movement.

The filming was disrupted by physical attacks and threats. Once it got done it had a lot of trouble being published, distributed. Lots of people fought it by various means. It was basically banned for a long time.

The story is about how worker solidarity and patriarchy can influence each other. People can be hypocritical and act very badly to their comrades (like their wives) even while talking a big game about being radical. Through struggle and holding each other accountable we grow and improve individually and collectively.

In case there's any doubt, its a really good movie and not just on political grounds. Just as a movie. It was created with so much care and love and skill and understanding.