Old SF story where a human helps defend Jovians agains human invaders

Question

This was an old English language science fiction short story I read in an anthology in a high school library sometime between 1962 and 1968.

In the 1920s and 1930s astronomers discovered that the giant planets - Jupiter, Saturn, Uranus, and Neptune, must not have solid surfaces that someone could stand on. Instead their atmospheres must gradually become thicker and thicker with depth until reaching stupendous density and pressure at the cores of the planets.

This knowledge took some time to be realized by a lot of science fiction writers and readers, and I have read a few stories in which the giant planets did have solid surfaces that lifeforms could walk on. Major science fiction writers published stories with solid surfaces on giant planets as recently as "Call Me Joe" by Poul Anderson, Astounding Science Fiction, April, 1957, and perhaps later.

The story I ask about seemed rather old fashioned in the 1960s.

In the story I ask about, Earth humans invade Jupiter, which has a solid surface. An Earthman defects to the Jovians, and aids them in their resistance to invasion (despite Jupiter in real life having 2.5 times the surface gravity of Earth, which shoud have incapacitated him).

Despite his help, the humans keep on winning, pushing the surviving Jovians farther and farther back, until there is only one small group of surviving Jovians left. As the Earthmen close in for the kill, the human protagonist explodes an atomic bomb or something, killing himself, the Jovians, and perhaps many of the attacking Earthmen.

Added 01-28-2022

So Edmund Hamilton's "A Conquest of Two Worlds" (1932), identified in John Rennie's answer, was in only one anthology early enough for me to read in that era, Every Boy's Book of Science Fiction (1951).

http://www.isfdb.org/cgi-bin/title.cgi?63333

And here is a link to a list of the stories in it.

http://www.isfdb.org/cgi-bin/pl.cgi?12676

Answer 1

A Conquest of Two Worlds by Edmond Hamilton.

The protagonist is Mart Halkett. At his court martial he gives his reasons for defending the Jovians:

INSIDE the great building Halkett stood up and heard his conduct judged. The officers who heard the case gave him a fair trial. His counsel argued ably concerning Halkett’s previous gallant record, the possibility of temporary aberrations and the like. Halkett might have escaped but for his own testimony a little later.

“I was quite in command of all my faculties when I ordered the atom-batteries not to fire,” he said quietly.

“Did you realize, Captain Halkett,” asked the presiding officer crisply, “that in so doing you were betraying your sworn oath?”

Halkett said that he had realized. “Then what reason can you give for your deliberate breach of trust?” Halkett hesitated. “I can’t give any reason that you’d understand,” he said.

Then he burst out with sudden white passion—“Why shouldn’t I have done it? After all, Jupiter belonged to the Jovians, didn’t it? What were we there but invaders, interlopers? How could I order those hunted flipper-men destroyed when all they were trying to do was to keep their own world?”

The story ends:

The whole interior of the great circular Jovian enclosure went skyward in a terrific series of explosions that wiped out not only all of Halkett’s Jovian followers and massed refugees but most of the Jovians and many of the earthmen fighting in the surrounding works. There was left only a huge crater.

“The dumps of atom bombs there in the enclosure!” cried Burnham. “A blast must have reached them and set them off!”

Crane nodded, his face strange. “Yes, a blast and in Halkett’s hand. He set them off to wipe out his Jovians rather than see them sent to the reservations.”

“My God!” Burnham cried. “That was Halkett’s way out for the Jovians, then——old Halkett——”

Crane looked stonily at him. “Didn’t you see that that was what he meant all the time to do? Give orders to round up those last Jovians in the works and bring them in.

“Then send this message back to earth. ‘Last Jovian base taken and renegade Jovian leader Halkett dead. Jupiter under complete control. Accept my resignation from Council Army. Crane.’ ”