a famous artist that does art of army?

i need to do some research of a legitimate artist that does something like this(i need it for homework):
http://features.cgsociety.org/newgallerycrits/g59/219459/219459_1187490817_large.jpg
when i mean legitimate, i mean something that a teacher will say yes to, last time i showed my research on a very good piece of artwork, but she scraped it and say, no internet artists
oh, but when i say war, i don't mean like super modern with tanks, cuz then i can't be "inspired" to make a piece of artwork (which is a scenery of army with bunch of spears)
something like that, but in colour
http://karenswhimsy.com/public-domain-images/persian-army/images/persian-army-4.jpg