'Oh! Jesus Christ! I'm hit,' he said; and died.
Whether he vainly cursed or prayed indeed,
The Bullets chirped-In vain, vain, vain!
Machine-guns chuckled,-Tut-tut! Tut-tut!
And the Big Gun guffawed.
Another sighed,-'O Mother, -Mother, - Dad!'
Then smiled at nothing, childlike, being dead.
And the lofty Shrapnel-cloud
Leisurely gestured,-Fool!
Owen is reflecting the centuries-old observation that soldiers on the point of death  cry for their mothers . Brutality and aggression is a veneer, and subconsciously these soldiers remain small, vulnerable boys.