As Marco says, there are many ways to translate "de tous les combats". You could certainly do it more literally: "fought in every battle", for example. But "être de tous les combats" is a set phrase, expressing the idea they could always be counted on to get stuck in and fight the good fight, as it were; at least, that's how I understand it. So I think a more hyperbolic, non-literal version like "in the forefront" is legitimate. But you could say something like "were involved in every fight". And I think "fight" would be perfectly OK instead of "struggle"; it's a matter of taste.

What I do think is important is the verb tense. "Seront" and "mèneront", in the future, follow from a historic present narration of past events. This is common in French but nearly always creates an unnatural effect in English, in my opinion. If you use past tense narration, as English naturally does, "will be" will logically become "would be" or "were to be". But even that seems awkward and unnatural to me. I think the idiomatic way to express this is English is with a simple past tense.

"Dont" means "including": every struggle/fight, including those that led to...

''In every nation of the western world, even in the nations behind the Iron Curtain, miners have been in the forefront of every struggle for social justice"
https://books.google.co.uk/books?id=WDNF_9eYszgC&pg=PA78&lpg...