The poem "Does it Matter?" by Siegfried Sassoon in many ways reflects his own disillusionment with war after his personal experience with trench warfare. Sassoon was awarded the Military Cross for his heroism, which included saving many wounded soldiers after a raid at Mametz. After he was wounded at the Battle of Arras, he suffered what was then called "shell shock" (which we would now call post-traumatic stress disorder), and became an anti-war activist. The tone of the poem is deeply bitter and sarcastic, displaying his resentment of people who expect badly wounded and maimed soldiers to maintain a cheerful and positive attitude about their injuries.
In the poem itself, we get an escalating sense of the types of damage war inflicts on soldiers. The first stanza describes a soldier with a missing leg, as people return from engaging in the sports he used to enjoy before his injury; the mood combines regret and resentment. He especially resents the way he is expected to feel grateful for the kindness of the uninjured.
The second stanza describes a soldier who has lost his sight in the war, sitting outdoors and feeling the light he can no longer see. While the mood is not explicitly stated, which is one of the great strengths of the poem, the image of a blind soldier facing the scenery he once loved in what appears to be the setting of a wealthy country house, evokes again both sadness and bitterness, and a sort of rage at the expectation that he should be grateful for other people's kindness, and act cheerful rather than despairing.
The final stanza makes the point that the worst damage is invisible, the mental damage from having experienced the horrors of war:
Do they matter?—those dreams from the pit?...
You can drink and forget and be glad,
And people won’t say that you’re mad;
For they’ll know you’ve fought for your country
And no one will worry a bit.
The bitterness, resentment, and despair deepen in this stanza. The kindness of people towards injured soldiers is viewed almost as a way of avoiding responsibility for having voted for the government that sent them off to war. The narrator especially resents the lack of worry, or moral responsibility, on part of the civilians who think that minor gestures of kindness can somehow absolve them of the burden of guilt for ex-soldiers whose lives have been destroyed. He also, as we can deduce from biographical information, was angry at people who dismissed his anti-war attitudes as the product of PTSD and refused to take him seriously.