"War is a brutal nightmare." The sentry is a poem that represents a explosion.

It shows and explain a explosion and he wrote his feeling about how he felt when he had to leave people behind." I see your light"  the poet used metaphor,alliteration, imagery,onomatopoeia, all to help him understand the big idea which is:" war is a brutal nightmare" the sentry is important in many reasons to make it important, he used alliteration, metaphor, imagery and so on. He used strong word such as, ghastly and horrific. He explains his feelings and what he sees using imigary of sight. In the sentry, the poet Wilfred Owen try's to make you understand the experience of getting bombed. 

Example