"Time Lag" is a short story by Poul Anderson.
On the planet Vaynamo, Elva is completing her circuit as the representative of her husband the Freeholder when their holding is attacked. She manages to get her infant son to an Alfavala — one of the marginally intelligent aliens of this planet — but her husband is killed, and she, taken captive. The fleet commander takes her as his concubine, and she tries to use the position to her best advantage, learning of how his overpopulated planet, Chertkoi, is conquering others for resources, despite using a slower-than-light travel (with relativistic Time Dilation).
- Arcadia: Vaynamo, rural, peaceful, and happy.
- Artificial Gravity: During the years before the final Chertkoi attack, Vaynamo develops gravitic-force weapons and gravity manipulation drives that allow their fighters to maneuver at dozens of Gs acceleration and run rings around the invaders.
- Bittersweet Ending: Elva loses a lot.
- Blue Blood: Elva and her husband hold some hereditary position.
- Damsel out of Distress: Elva never fights, but her resistance is unending.
- Dead Guy Junior: Elva learns of one at the end.
- Disproportionate Retribution: The attack at the beginning is one of several, to wipe out villages because the planet resisted.
- Do with Him as You Will: Elva's people offer to punish Bors in any way she sees fit. She tells them to just shoot him.
- The Empire: Chertkoi has conquered many planets already.
- Evil Cannot Comprehend Good: Why not just dispossess the Alfavala?
- Feudal Future: Power is hereditary.
- Fish out of Temporal Water: Her rescuers quickly assure her that she's welcome, even though she's now younger than her own son.
- Happily Married: Elva in the opening
- Happiness in Slavery: Elva convinces Bors she is happy. Its a sign of his limited world view that he believes it.
- Hooked Up Afterwards: One fellow prisoner hopes she will let him visit at the end.
- Luke, You Are My Father: In "Time Lag", Elva is told by another of her rescuers that one of them is her grandson; then he immediately takes her hands.
- Moral Myopia: Chertkoi, apparently. Bors embodies it, not even comprehending resistance.
- Moses in the Bulrushes: Elva sends off her son from the attack.
- Non-Idle Rich: Elva and her husband.
- People of Hair Color: Vaynamo is inhabited by blue-eyed blonds — with slanted eyes, to tweak the Phenotype Stereotype.
- Population Control: Vaynamo has stablized its population; Chertkoi regards them as hoarding resources.
- Rock Beats Laser: Defeat by the rural Vaynamo, lacking in industry, astounds Chertkoi. Averted in the final battle, which Vaynamo wins by straightforward technological superiority.
- Sex Slave: Elva is picked out as a concubine.
- Servant Race: The Alfavala have chosen this role.
- Thicker Than Water: Elva is told at the end about how her son survived, and has descendents, so that she is not alone.
- Time Dilation: Elva ends up only a few years older, while her infant son is now old, and indeed, has an infant grandson.