The last two lines really made this poem for me- you perfectly encapsulated everything in those six words. I thought the rest of the poem was good, without ever really scaling the heights that you managed at the end (although I did like 'shattered growl').
I can only suggest trying to maintain that level of intensity throughout the whole poem- it's difficult, I know, but I think you'd really be onto something if you did.
Also- a few grammar/spelling things need to be fixed ('stubgorn'? 'his eyes/hides'?), but that is only a minor consideration.
This is wonderful! I sense so much pride in your writing, and rightfully so. All of us owe so much to the war veterans, particularly the ones who saw combat. I offer a heartfelt "thank you" to your grandfather, and another to you for writing this excellent piece!
It has been awhile since I commented on here but, it is nice to return to some good sound writing that allows the writer to see into the mind of the writer. Your grandfather is a proud man as he should be and for you to recognize that says that you are in tune with him.
Again, Nicely done