Death
Death is personified in this poem and even sits at the table with the speaker and his friends. The speaker even describes death as an "old chum." From this, we gather that the speaker has become so accustomed to the presence of death in his life that he is now desensitized to it. Still, he remains upset by its violent arrival and its distressing aftereffects. Yet the speaker's friendly attitude towards death isn't just proof of death's constant presence during wartime. It is also an implicit suggestion that death itself isn't problematic. In fact, the personified death comes across as somewhat helpless in this poem, causing pain with its every cough. The speaker's relative sympathy for death only serves as more of a condemnation of humans, who consciously cause war, violence, and pain.
Nationalism
The speaker concludes the poem by mocking soldiers who repeat idealistic narratives about war. Though these narratives might insist that wars are fought in order to protect people and keep them alive, this isn't actually true. The speaker instead argues that wars are always fought for the sake of "flags"—and flags, in this case, are symbols of nationhood. At the heart of this critique is the distinction between "men" and "flags." Rather than accept the idea that people are represented by their nations, and therefore stand to benefit from wars fought on behalf of the flag, Owen proposes that members of any individual nation can and do suffer when the abstractions of nationhood are granted more importance than the concrete needs of people.
War
War is portrayed in this poem as the natural meeting point of death and nationalism—a process by which powerful people choose to sacrifice actual humans for the abstract ideal of a country. Owen lays out this stance with an almost mathematical formula in the poem's final lines, describing exactly what war is not fought for—lives and men—and what it is fought for—flags, which symbolize nations and nationalism. Indeed, the speaker implies, the only reason anybody willfully fights in a war, given their futility and the risks involved, is because they have been deceived about the purpose of the war. This deception means that another, "greater" war will arise, with a new generation enthusiastic about its supposed purpose.
