i need the introduction about the peom called dulce et decorum est?

This is not the forum for essay writing, but you can use this idea.  The poem has to do with the horrors of war, especially during World War I when gas (mustard) was used as a form of chemical weapon against the enemy.  It tells that men who are not involved in the war makes the rules for the soldiers and uses a Latin line from a poem by a Roman poet (the title) meaning "it is sweet and beautiful to die for one's country."  There is irony in this line since men who are fighting are not the ones who have this philosophy.