For your purposes as video game music, you seem to have done a pretty good job, and I could definitely see this in a military style rpg. That being said, for the first half of the song (up until about 1:12) the composition seemed a little stagnant and muddled. It could definitely use a little more variety, as a gamer could get pretty tired of that same march of the brass. I really liked some of the melodic ideas you had, like that bit between 1:17 and 1:30, and from there you play around a little more rhythmically, which was nice, but it would be better if you developed some of those melodic idea a bit more.

As for the instrumentation, I think it's pretty good, but that low brass really could get annoying if this is playing on repeat.

All said and done, it's a fine composition, and good luck with your project

- R4R