We'd found an old Boche dug-out, and he knew,
And gave us hell, for shell on frantic shell
Hammered on top, but never quite burst through.
Rain, guttering down in waterfalls of slime
Kept slush waist high, that rising hour by hour,
Choked up the steps too thick with clay to climb.
What murk of air remained stank old, and sour
With fumes of whizz-bangs, and the smell of men
Who'd lived there years, and left their curse in the den,
If not their corpses. . . .
There we herded from the blast
Of whizz-bangs, but one found our door at last.
Buffeting eyes and breath, snuffing the candles.
And thud! flump! thud! down the steep steps came thumping
The moment of contemplation, during which we share Owen’s fears, is ended when he draws the reader back to the present. 
 The word ‘herded’, as with ‘den’ suggests animals …no doubt many men felt they were treated no better. 
