Second Night of Summer

Humanity has been at war with the Halpa for countless centuries. Once in every several centuries, conditions are right for the Halpa to launch an attack on a single planet; then, humanity must either repel the attack or destroy the planet utterly, to prevent the Halpa from gaining a foothold.

This time, the attack is coming on the planet Noorhut, and Grandma Wannattel is the agent of human interests tasked with repelling the attack. Should she fail, the planet--along with her and all of the rest of the planet's inhabitants--will be destroyed.

With the (unknowing) aid of a young boy named Grimp, the attack is repelled, and Grandma Wannattel opines that Grimp may one day take her place as defender of Noorhut.

Notes

This is part of a series by Schmitz. The other three stories in the series appeared in Astounding.