Couple of stories

Both are online, via scans of Astounding (British Edition), June 1958 where they were reprinted. One is online elsewhere too.

While both are ordinary, they also have something special going for them:

1. "Second Game" kept me fascinated & reading all the way through, though I didn't really find convincing the point it made.
2. While I personally found "Try and Change the Past" forgettable, I've seen others refer fondly to the series it is part of (series includes at least one novel, serialized in Galaxy simultaneously with publication of this story).

Here are the stories:

1. [novelette] Charles V DeVet & Katherine MacLean's "Second Game" (B): When a much smaller & powerful country invades & totally crushes your country, you're still a winner because, over a few generations, you will absorb the enemy in your gene pool! While something similar has happened more than once in India's history, I find the idea of counting it as a win totally absurd.
   
   Game part of the story comes from a chess-like but far more complex board game. Velda, the small invader in the story, a world of human-like beings, is crazy about this game & your skill at the game determines your social rank. The invaded, in the story, is the galaxy spanning human empire called Ten Thousand Worlds Federation.
   
   Story is told through the eyes of a human spy sent to Velda. Velda has repeatedly rebuffed the human contact but humans persist in trying to "persuade" them, eventually precipitating the doom.
2. [ss] Fritz Leiber's "Try and Change the Past" (B); read online or download (need to scroll down the page): A man is rescued from death by "Snakes", fighting the "Change War" with "Spiders" across space & time, with the intention of recruiting him as a time soldier.
   
   He figures if he could go back & change miner details near his end, he would not only live but escape from Snakes. Only the nature's law of "Conservation of Reality" prevents any significant postponement of his death...
   
   PS: I could not figure out how Snakes were able to circumvent the law of "Conservation of Reality" when they recruited him in the first place!