I don't understand the meaning of one sentence in Wilfred Owen's sonnet titled On Seeing a Piece of our Heavy Artillery Brought into Action:
Be slowly lifted up, thou long black arm,
Great Gun towering towards Heaven, about to curse;
Sway steep against them, and for years rehearse
Huge imprecations like a blasting charm!
Reach at that Arrogance which needs thy harm,
And beat it down before its sins grow worse.
Spend our resentment, cannon,-yea, disburse
Our gold in shapes of flame, our breaths in storm.
Yet, for men's sakes whom thy vast malison
Must wither innocent of enmity,
Be not withdrawn, dark arm, the spoilure done,
Safe to the bosom of our prosperity.
But when thy spell be cast complete and whole,
May God curse thee, and cut thee from our soul!
I understand the first half of the sentence as:
Yet, for the sake of men whom you must subject to shelling ("wither") until they are "innocent of enmity" (cease to feel enmity?), do not withdraw, oh the piece of artillery ("dark arm").
But what is "safe to the bosom of our prosperity"? Do not withdraw in safe condition? What is "bosom of our prosperity"?