Rereading the Third Story I began to wonder:

What happens if Blacken Prime is hit by a stealth Acid Rain attack?

Let's consider the scenario where you drop a missile from orbit during peacetime. Assume its payload is sufficient to neutralize enough oxygen that the planet will become uninhabitable to Terran life.

Blacken Central Command orders general lockdown; 20,000 civilians outside head for cover.

Blacken Central Command intercepts missile. Missile explodes; chemical agents initiate mixing, creating a purple cloud of doom that rabidly consumes any oxygen it can find.

Automated systems detect a potential biowarfare or chemical warfare agent has been released. All properly equipped buildings automatically seal off ventilation systems and lock down entrances as the blast wave approaches. Somewhere between 1,200 and 9,600 civilians are trapped outside; they succumb to Acid Rain's effects within ten seconds of initial exposure.

What transpires next depends on whether or not Blacken is on good terms with the Talus Republic. If so, Blacken Central Command immediately opens communications with the Talus, requesting assistance.

Because the Talus Republic is tied up with its own wartime responsibilities, they cannot send direct assistance. Blacken Central Command orders its military robots to full alert and begins dispatching robotic engineers to attempt to clean up the Acid Rain agent. This proves fruitless, as the weapon's effects are rolling across the entire planet. Settlements Two and Three have already been warned and are in a state of lockdown; civilian casualties in these settlements will be minimal.

The Cy'tan settlements have been warned by this point by automated systems and will take whatever measures they consider necessary. They sustain an unknown number of casualties.

By this point, the Acid Rain has swept across the planet and caused the deaths of anyone caught outside - anywhere from 1,250 to over 10,000 Terran civilians - and rendered the planet uninhabitable. Blacken Central Command, noting this, will order a general evacuation of the planet, airlifting detachable structures directly through the gate to Earth using the massive UEF Continental-class heavy transports, and ordering occupants of immobile structures to don hazmat suits and report to the nearest evacuation processor. Because of accidents during the evacuation process, up to 250 civilians will be killed by asphyxiation due to the depressed oxygen levels and remaining Acid Rain in the environment.

It transpires from preliminary intelligence that the Kallum-controlled Talus Empire is responsible for ordering the strike. Immediate retaliatory response is authorized by President Riley, since UEF civilians and military personnel have perished in the strike. A massive UEF fleet is gated through from Earth and immediately jumps straight to Kalnoky Prime, engaging the Imperial garrison with deadly force.

Total deaths: up to 12,000 Blacken and UEF citizens on Blacken Prime, untold UEF and Talus naval personnel; severe weakening or total defeat of the Talus Empire fleet allowing the Talus Republic forces to achieve naval superiority over Talus territory.

You could inflict more casualties by having a sleeper agent, e.g. a Morna-like figure, cause a detonation of an Acid-Rain munition set on the surface. This would cause the deaths of up to 30,000 civilians and a complicated investigation, putting the Alliance out of the picture just long enough for the Talus Republic to collapse to a multipronged decisive strike.