The Wound Dresser, by Whitman

      In this poem by Walt Whitman, the narrator is a wound dresser, that is doing his work after a battle that took place. This man has a realization while he is working on these men, and it makes him change his mind about the war. At first, he wanted to wage this war, he was almost excited about it. However, after seeing these men injured and hurt, he changes his mind about this. He sees the suffering these men are going through and decides that he does not think this war is worth it. He also states that in both sides of this war the fighters are brave, and on both they are dying.
      In the poem the wound dresser thinks to himself, that he wants their death to come. He says "In mercy come quickly" meaning that the faster their death comes, the better. This is because these men and boys are suffering so terribly that it would be more peaceful and humane for them to simply die. They are in agony and he also says that he would die for them if he could in order to save them. This is touching in the way that it reminds one that doctors do in fact care about their patients. We're not just numbers to them, we matter. They want to see us live and they hate to see us suffer.
      This poem is very descriptive, so i would like to know, is this poem entirely made up, or an actual memory from Whitman?