What are some really well known war poems?

Hi guys, i was just wondering if you guys know and really great poems on Fighting in a War and war its self? I know that In Flanders Field's is really well known but i was wondering if you guys could provide me with some other really good war poetry? I have a school project coming up in which i have to write war poetry and i just want to get an idea on how some of the greater war poems are written. Thank you, your help is greatly appreciated =).