What passing-bells for these who die as cattle?
Only the monstrous anger of the guns.
Only the stuttering rifles' rapid rattle
Can patter out their hasty orisons.
No mockeries now for them; no prayers nor bells,
Nor any voice of mourning save the choirs,--
The shrill, demented choirs of wailing shells;
And bugles calling for them from sad shires.
What candles may be held to speed them all?

 What follows is the metaphorical “choirs”, the first human, the second the disharmony and cacophony of ‘wailing shells’.  No  amount mourning or wailing from family and friends will drown out the sounds of machine guns firing.