teleportation - Story Identification: interplanetary war won by teleporting bombs past force fields

I'm trying to find a story for my father, from the 70s or earlier

Earth is at war with aliens (possibly Martians) and was unable to effectively fight back as the aliens had planetary (or at least city-protecting) force fields through which no bombardment was possible.

Earth eventually wins through invention of a device that allows them to teleport weapons (nukes?) under the force fields.

originally believed to be one of Harry Harrison's 'One step from earth' shorts, but this is not the case.

Thanks in advance for any help here!

Answer

It's not a perfect match (no force fields), but I think the story you want is "Loophole" by Arthur C. Clarke, first published in Astounding Science Fiction, April 1946, available at the Internet Archive.

Here is a plot summary from Wikipedia:

The story begins in the form of correspondence between the President of Mars and the Secretary of the Martian Council of Scientists, regarding the discovery of atomic power (in the form of atomic bombs) by humans. They are concerned that once humanity's current war is over (they have been monitoring Earth's broadcasts), humans will use atomic power and rockets to breach interplanetary space and pose a threat to Mars. A remote monitoring station is set up by Mars on the Moon to monitor Earth's progress. Finally they send a fleet of 19 battleships along with a warning to Earth that one city will be destroyed every time a rocket leaves Earth's atmosphere. Earth agrees to stop experimenting with rockets when they realize their broadcasts are being intercepted. Ten years pass without any further rocket experimentation, while the Martians secretly plan for the extermination of the human race, recognizing that Earth will inevitably become a threat to them in the future.

The next letter, beginning "Mars is a mess!", is sent from Mars by a human named Lieutenant Commander Henry Forbes, and reports to Earth upon the destruction of Martian civilization due to a nuclear attack from Earth. The previous letters had been recovered from the ruins of the capital. Rather than experimenting with rockets, humans had perfected matter transmission and beamed their bombs directly over the Martian cities. Forbes is hopeful that rocket experiments will resume soon, as he finds being "beamed" across space to be uncomfortable.

There is a review at this Arthur C. Clarke Fansite.