No mockeries now for them, no prayers nor bells; (5)
The second half of this line is where we find out how critical our speaker is of religious ritual. Before this, we might have thought he was just missing those passing-bells, wishing they had some at the front to honor the soldiers. And the way the line sets it up (giving us "mockeries," then having us find out that those mockeries include prayers and bells) makes the line that much more shocking, and lets us know that our speaker is really going to let it rip. Religious rituals as mockeries? Owen sure isn't pulling any punches here.
Nor any voice of mourning save the choirs, – The shrill, demented choirs of wailing shells; (6-7)
This line is a little bit of a sucker punch, too. We hear about the choirs and we picture a choir in a church singing a beautiful hymn to mourn the sacrifice the dead soldiers have made. Then we find out that the choir our speaker is referring to is actually the freaky noise made by incoming shells. Our speaker might be suggesting that this is the very same sucker punch that soldiers get. They hear all the pomp and rhetoric, the prayers for victory. Then when they arrive in the war zone – oops! Dying for their country is a little more awful, and senseless, than it first sounded.
What candles may be held to speed them all? (9)
Since our speaker has already let fly with his critique, the emotion here is clearer than in the first line of the poem. There's still the sadness and the sympathy for the soldiers, but there's an unabashed cynicism when it comes to passing-bells and candles. Sure, it's sad that these soldiers have died, but according to our speaker, the way we mark that sadness is just, well, ridiculous. Mainly because it's pointless. The pomp and circumstance of public, religious mourning just doesn't jive with the cattle-like deaths these men endure.
Not in the hands of boys but in their eyes Shall shine the holy glimmers of goodbyes. (10-11)
Our speaker suggests that we shouldn't look to candles or flowers to hold any bit of holiness. The real expressions of mourning, such as the tears in a dying soldier's eyes (or, say, in the eyes of his son), are where we might find something that resembles holiness. Could that be the mourning that goes on behind those lowered blinds in the last line?