pow says thank you to guard and then drops dynamite

I think in an earlier scene the guard had beat or whipped the prisoner for not saying thank you for something and in this latter scene the pow approaches the same guard and says thank you 2 or 3 times and drops a box of dynamite killing them both in the explosion and maybe some other guards. Can't believe I have forgot this as I remember the scene quite vividly and the look on the prisoners face .. they are outside on some kind of quarry, the guard realise what is going to happen but it is obviously too late.. please somebody tell me what this movie is

POW implies a war. WW2? what were the races of the prisoner and guard?

From scene I remember I guess is a war film.. I remember the POW is white male and I think the guard is too but not entirely sure

In general, armies wouldn't give their prisoners access to dynamite, so I don't think it's a WW1, WW2, Korean War or Viet Nam War movie.

I'd lean towards a Mexican movie, possibly.

There is Duck, You Sucker during a Mexican revolution, but I don't remember a scene like you describe.

It isn't that... I think they were working with the dynamite.

This sounds similar to King Solomon's Mines (1985) where Qartermain yells, "I got it" and throws the dynamite at the bad guy and blows him up.