When I uploaded my poem, I knew it was complex to understand (as told by many reviewers) so I'm going to clear a few things up.
The poem's Line 'Across the Ocean' shows Heero is fighting far from home.
'Down A River of Red' Tells of the blood that he has shed, the innocent lives he has killed and what he knows of War.
Now that the Living out number the dead, I am One of May.' This means it a war your only important once your dead, when you are alive you are one of many and so to be something you must die. Heero believes he is only something when he dies.
Thus, this poem shows that war is nothing, and will always be nothing if the only way to find value of a person in a war is to let them die.
I hope that clears a few things up for you, Bye!