I think the most emotional war poem is A Soldier's Song by Stephenie Tucker. This poem captures everything that is emotional about war. The loss of life and the loss of youth. It repeats the stanza "seventeen and full of rage" over and over again, expressing the constant battle with internal rage the soldier was feeling.
The soldier was feeling pain and then inflicted pain, causing a cycle of misery. Towards the end she writes that the soldier "spent all his love on weapon's kiss". I find this the saddest part of the poem because not only does the soldier lose everything, he loses the potential for love and love is the only thing worth fighting for.