Terrible As An Army With Banners

What is the story here? The sky is burning, and lightning splits the blackness of the night sky. There is a terrible army flying red banners, the colour of the blood they intend to spill, and they swarm into the city that they intend to lay waste to.

The city inhabitants have come out of their houses, but they are a crowd, with no weapons or fighting skills. They have no leaders and have no place they can go for safety or sanctuary.

They know they will see the morning either dead or in chains.

Their prayers had no effect.