I'm not sure if it is set in a universe of one of author's existing works. Guessing, because ending completely escaped me. Rest of the story was quite readable - leading up to (but not including) the climax.
His commentary on cities & their dwellers, however, was something I could identify with. It very much applies to Bombay, & probably a lot of places in India & elsewhere.
Story summary.Some world - apparently human inhabited. Militarily powerful religious fundamentalists control a place called Saarmara somewhere on this world. For a long time, they've been on a killing spree - destroying whole cities to establish "New Faith, the Word of the Prophet."
They've finally reached the City of Astralis. City isn't competent to defend itself. Its inhabitants are evacuated to a safer far off place. Except the man in the story. He intends to unleash some sort of weapon too terrible to contemplate by his fellow citizens.
What I'm not clear about is where the weapon got unleashed - on Astralis or on the enemy? Probably Astralis (making the invaders conquest meaningless - "Saarmarans will never take Astralis"), since it's still intact though "lifeless" "for millennia." May be some sort of radiation weapon that doesn't blast.
Story makes a reference to "paladins" - so may be familiar with those stories (of Bujold?) will help. This is my first Modesitt story.
Fact sheet.First published: Jim Baen's Universe, #17 (February 2009).