You can discover a lot about a poem by comparing it to one by another author that deals with a similar subject. You could compare features such as theme, form, structure, rhythm, language and figures of speech.
The key thing to do when comparing poems is to note the points where they are similar and the points where they differ. You could make a list noting similarities and differences between the two poems.
Comparison of 'The Destruction of Sennacherib' by Lord Byron and 'What Were They Like?' by Denise Levertov
The two poems look at the effect war has on a particular nation and specifically at the aspect of loss.
The after-effects of war are seen as ongoing and affecting others, beyond those who were engaged in fighting.
Both poems were written at a time when war was dominating the news – Byron’s towards the end of the Napoleonic Wars and Levertov’s during the Vietnam War.