Final answer:
Edgar Derby's life is marked by irony as he survives the perils of war only to be executed for a minor act, highlighting the absurdity of wartime justice.
Step-by-step explanation:
The irony of Edgar Derby's life is that after surviving the horrors of World War II, including the firebombing of Dresden, he is executed for the seemingly trivial act of looting a teapot.
The disproportionate consequence for such a minor transgression, after enduring such extreme circumstances, speaks to the absurdity and tragedy of war. This irony emphasizes the randomness of death in wartime and the often arbitrary nature of justice.