The first bit of fascination comes up in the forward to the story -- Pluto is described as one of the gas giants, like Jupiter and Saturn.
Pluto was discovered in 1930 and it was the second scientifically discovered planet. The first, Neptune, was discovered because the observed orbit of Uranus wasn't quite what was predicted. It was perturbed, and looking where a perturbing force might have come from discovered Neptune. Hot Dang! Looking more closely at Uranus's orbit suggested another possible perturbation, and searching for that one turned up Pluto. Double hot dang! At the time of this writing, early 40's, Pluto was still thought to be a gas giant planet. It had to be big if it was causing the perturbation.
But as Pluto was observed more and more, it turned out to have nothing to do with the 2nd Uranus perturbation (that, it turned out, was a mistake in observations, not real) and calculations of Pluto's size kept producing smaller and smaller results -- it is now thought to be one fifth the mass of the Earth's moon. It turned out that finding it was pure luck and in 2006 it was redefined as a dwarf planet, one of dozens circling the sun beyond Neptune.
But at the time of this story it's a big planet, and this story is about living on a big planet.
Interesting, I'd forgotten that this is a war-analogy story.
Gregor, the author, faces a problem which in my opinion he does not solve well. The problem is how to describe these alien men living on the surface of Heavyplanet, as he calls it. He uses a lot of adjectives comparing them to earth people such as "granite-hard muscles". But he is describing from the alien's perspective. Wrong, these are just normal muscles to the alien. But... it's a difficult challenge. I'll forgive. Less forgiving is that this alien can see the sun. Sorry, sun is hidden by dozens of layers of clouds -- can't forgive this.
He gives some sense of the pressure of the surface, but not nearly as good as the Ooze Zone I came up with.
Gregor tries, but he's sacrificing a lot of science reality to make the story happen. First, the classic 30's oversight of having a space ship that lands on a planet surface. This time in spades because it's a gas giant surface.
More point of view mistakes: This alien feels trapped on his planet by its crushing gravity. No. The alien grew up there. It's gravity is no more crushing to him than Earth's is to humans. Second, in a world shrouded with clouds, one where even the sun is not visible, why is this man thinking, longing, for star travel? And feeling urgent about the need. Nope. Does Not Compute.
And it gets worse. We have the magic of atomics. And the statement that chemistry doesn't stand a chance of providing enough energy. Chemistry can't even produce an explosion at this high pressure.
Hmm... This thinking comes from dealing with high pressure gas deep in the liquid ocean on Earth -- experience in submarines. But if the environment is supercritical -- too highly pressurized to support a difference between gas and liquid -- then an explosion produces no gas. However, I think a rapid change in volume due to a rapid change in energy state can happen -- an explosion. But, rather than a colorful and expanding out of hot gas and smoke through lots of volume, the explosion would be a nearly invisible shock wave. It would be more like a hammer hitting a nail. I haven't thought this through fully. How an explosion would create damage in this supercritical atmosphere and what that damage would look like would take more thought.
One other thing Gregor is not clear about is the relation between crushing pressure and crushing gravity. I suspect that the force of gravity pushing down on stuff in this environment is small potatoes compared to the crush of pressure on all sides. In both cases this crush will drive life to create bodies of neutral buoyancy, comparable to what sea creatures on Earth maintain, such as jellyfish. And, once again, this alien is not going to notice the crush any more than we notice being crushed on all sides by 14.5 PSI Earth atmosphere.
Let me note: I'm bringing up a lot of complaints, but I like the story. Gregor is trying. He's at least exploring. It's a good first step.
Now comes a plot twist human readers can easily relate to: A war between nations -- good and evil ones. This being written in WWII war years, the twist is not the least bit surprising.
He tries to explain how the ship got there: a disaster in a space battle and a wild jetting away... far, far away. ...It's weak.
Interesting... this is well before lasers so no one knew what to call ray-based weapons. They were imagined, but so far from implementation that anyone could call them what they liked. Gregor chooses projectors.
Ah... now the story turns into a typical clever spy against stupid enemy soldiers story. Ah well... worse, he constantly refers to water beating hard upon him -- real water. As stated earlier, if this is a supercritical environment there is no surface and no gas/liquid difference. This is now getting a bit annoying.
Another interesting expression: actinic light, apparently UV or above. Looked up the definition and it means capable of causing photochemical reactions. Sounds similar to but not quite as vigorous as ionizing radiation. It's impressive how much the technical language has changed in seventy years.
In the end, more disappointing than I expected: It's a WWII-era contemporary spy versus soldiers story with a bit of heavy planet slathered over the top. It makes me real glad I wrote Pressure Point, because it's a better treatment of this same challenge.