Already happened: Russia did that:

With thanks for a Fortean Message Board comment:

https://forums.forteana.org/index.php?threads/proxy-warfare-using-robots-drones-etc.69111/post-2364698

On-board gun

edit

The Salyut 3, although called a "civilian" station, was equipped with a "self-defence" gun which had been designed for use aboard the station, and whose design is attributed to Alexander Nudelman.[1] Some accounts claim the station was equipped with a Nudelman-Rikhter "Vulkan" gun, which was a variant of the 23 mm Nudelman aircraft cannon, or possibly a Nudelman NR-30 30 mm gun.[12] Later Russian sources indicate that the gun was the virtually unknown (in the West) Rikhter R-23.[13] These claims have reportedly been verified by Pavel Popovich, who had visited the station in orbit, as commander of Soyuz 14.[12] Due to the potential shaking of the station, in-orbit tests of the weapon with cosmonauts in the station were ruled out.[1] The gun was fixed to the station in such a way that the only way to aim would have been to change the orientation of the entire station.[1][12] Following the last crewed mission to the station, the gun was commanded by the ground to be fired; some sources say it was fired to depletion,[12] while other sources say three test firings took place during the Salyut 3 mission.[1]

I believe that's Soviet Union. And there is no records of weapons other than one commander's word

More importantly, it's explicitly excluded by the resolution criteria

Based on the requirement that the station needs to be manned by military personnel, this is a clear no. The consts and risks of putting people in a military satellite far outweigh the benefits.

@MikeAckermann same could be said about submarines. underestimating the sheer human instinct of expansion.

@notarealuser that was a quick response

Getting signals into space is as far as I know easier than into deep ocean, but still a good argument.

How will you resolve "no countries will do so;" does the market have a set timeframe?

@GazDownright By the end of this decade. After which the Resolution date could be extended(lol in 2030) if any credible reports of future plans of this nature exist.

@notarealuser this is unobvious rule. Add please to the description.

Without it, if you leave manifolf, moderator might resolve the market prematurely in 2030.

Better have a fixed or not have an end at all, than a sliding one. Brings a lot of ambigious cases

@KongoLandwalker 🫡

How does this interact with the military space stations the Soviet Union built before?

@JoshuaWilkes question says "will build", so only events after the market opening count. Unless creator made a mistake

@JoshuaWilkes To my understanding none of the planned missions of Soviet Union's military space stations were carried out to success. At least not success by definition of the Resolution Criteria for this market.

@notarealuser

https://en.wikipedia.org/wiki/Almaz two of them definitely were. I think it would be best to add a line as Kongo suggests ~

Bet on which country will first build a military space station.