Theodore Cogswell's "The Spectre General" (novella, military sf, humor): Neither is complete, till they come together!
A spaceship maintenance battalion of its military got stranded on a front world, now long forgotten & isolated. But in a funny variation of "A Canticle for Leibowitz", they carry on the tradition of teaching spacecraft & machine maintenance to their kids, & maintain a sort of military discipline, though the society has fallen to primitive agrarian levels & no one thinks the machines they learn to fix can actually do something.
Elsewhere, a military version of empire has come up, next in command always intriguing to unseat the current ruler. Current ruler denies technical staff to commanders who could potentially unseat him, to keep them weak.
So we have a military commander with fleet falling apart & no one to fix things. And an isolated world of trained maintenance men who don't even believe the machines they can fix can do anything useful. Results should be interesting when the two parties meet...
Fact sheet.First published: Astounding, June 1952.
Among the stories in Astounding/Analog issues edited John Campbell.