he gives us a window into the past, he explains vividly how the attack happened and the most amazing thing is that he wrote it in hospital after he was wounded in the very gas attack he describes in the poem and after his hospitalization he goes back to fight in the war and ended up dying in it. Both world wars brought out the best writers,poets, heroes, politicians and people that's why they are called the worlds greatest generation because they were fearless and selfless humans and that's why his poem can bring tears to a dry eye.