The darkness crumbles away.
It is the same old druid Time as ever,
Only a live thing leaps my hand,
A queer sardonic rat,
As I pull the parapet's poppy
To stick behind my ear.
Droll rat, they would shoot you if they knew
Your cosmopolitan sympathies.
Now you have touched this English hand
You will do the same to a German
The poet begins to address the rat, who is now ‘droll’, a sardonic example of  anthropomorphism . A rat doesn’t have a human sense of humour. 
 This echoes the style of John Donne, who would address the ‘unruly sun’ or the flea in the  poem  of the same name.
Break of Day in the Trenches