"Five Ways to Kill a Man" by Edwin Brock describes, in almost cold clinical language, the history of humanity's inhumanity by presenting us with five different episodes in human history. It expresses an apocalyptic theme in which the advancement of human technology results in increasingly more brutal and efficient ways of killing.
The first stanza portrays the crucifixion of Jesus Christ. Its position is thematically significant, as Jesus is held to be a figure who brought "peace on earth" and in theory the martyrdom of the founder of Christianity should have made Christians more humane.
Instead, in the second stanza, we encounter the European Christian Middle Ages, in which the traditions of jousting and chivalry masked equally brutal and pointless killing.
The third stanza recounts the horrors of mustard gas used in World War I and the fourth stanza describes the nuclear bombs dropped on Japan by the United States.
The final stanza is the climax to the poem, suggesting that humanity's destructive impulses will lead us to self-destruct as our technology fails to give us peace and provides us instead with increasingly lethal ways to destroy ourselves. Thus the theme of the poem is that our "advances" have led us not to be better people but more lethal killers.