I am usually the first person to say that I do not really care for poetry, and I can say that reading and attempting to understand The Waste Land did not change that at all. At the end of reading this, I thought I had finally come to the realization that this was about World War II. Which was great... until I realized that this was written before World War II had even begun, which I thought ruined my entire understanding of the work; however, I actually think it makes it stronger. Eliot knew that war is cyclical and will happen again, which he predicted correctly because World War II did happen about 17 years after The Waste Land was written, which gives this work more credibility.
Throughout the poem, Eliot warns that war and violence is a cyclical event (e.g. the pearl eyes of the drowned Phoenician Sailor). The last six lines of section one, specifically, is a warning against letting war happen again and the part you play in it. "Oh keep the Dog far hence, that's friend to men, Or with his nails he'll dig it up again!" The dogs of war are 'friends to men' because men (read: people) have a tendency towards violence and war, so we must be careful and dilligent in keeping that tendency buried and not let it be dug up again. I like that it kind of brought the reader into it and made them, us, responsible for keeping the peace too.