Expanding upon the Eridani Edict
The comment came up as part of a thread on Apollo counters and uses, thereof, following exchanges about using Apollo to slaughter your targets from beyond the Limit, was - and we quote - "Fleet then avenges destruction of planet WITH UNSTOPPABLE APOLLO LAUNCH against system which initiated said violation of Edict - with Edict as full justification of retaliatory strike."
Okay, the quoted portion of this question suggests to me that there's still a fundamental misunderstanding of what the Eridani Edict is designed to do and what it actually says.
First, the purpose of the Edict is to prevent the routine destruction of planetary populations, whether in the name of military expediency, fanaticism, or vengeance. The Edict isn't really concerned with why someone might want to exterminate a planetary population, and it recognizes that in a universe equipped with fusion weapons, kinetic weapons, biological, chemical, nanotech, and even (potentially, at least) genetic weapons, there are going to be "atrocities" no matter who tries to prevent them. The Edict is concerned with limiting strikes on inhabited planets which inflict massive casualties; its drafters weren't foolish enough to think that they could hope to eliminate such strikes altogether.
As I've said before, the Eridani Edict is to the Honorverse very much what the generally accepted "laws of war" were to 18th and 19th century Europe. The warfare of the previous couple of centuries in Europe, especially the wars fought in Germany in the 17th century, had been marked by massive destruction, massacres, atrocities, and just about every form of brutality one could imagine. Following that period, the nation states and armies of Europe developed an accepted "code of conduct" for military operations. That code, those "laws of warfare," attempted to set limits, to establish protocols. For example, you were permitted to do things to the civilian population in one of your own "rebellious provinces" which you were not permitted to do to the civilian population of someone else's provinces. (This, by the way, was a point which William Sherman -- boo! hisss! -- made to those individuals who protested his activities on his little march through Georgia and South Carolina. In his view, those states were "rebellious provinces," and that meant the rules under which he had to operate were different. Since his side won, his interpretation stood up in the end.)
The specific "law" from this period which serves as the basis for the Eridani Edict is, in many ways, the rule of the "practicable breach." Basically, the "practicable breach" was a breach in the defenses of a fortress or a fortified town through which the attackers could launch a decisive attack. It meant, in effect, that the defenders' position had become ultimately hopeless unless they could be relieved by a friendly field army before the aforementioned decisive attack could be organized and launched. They might be able to continue to resist, and to inflict additional, possibly massive, casualties on the attackers, but they could not hope to hold their position in the end. When that became true, they were required under the "laws of war" to surrender, and the attackers were required to guarantee their honorable treatment and allow them to surrender upon reasonable terms. All very civilized.
But if the defenders refused to surrender after a practicable breach had been achieved, then the attackers were fully justified in allowing the defenders no quarter and putting everyone of them to death after the fortress was finally taken. In the case of a fortified town which continued to resist beyond the point at which it was "required" to surrender in accordance with the principle of the "practicable breach," the attackers were fully justified in sacking the city, with all of the rapes, murders, and associated atrocities that was bound to produce. This was justified on the basis that the defenders' continued resistance could not affect the ultimate outcome of the siege or the assault -- the fortress was going to fall -- and that their only purpose at that point could be to inflict as many casualties on the attacker as possible.
The Eridani Edict has some points in common with the rule of the "practicable breach." Essentially, the Eridani Edict says that no star nation may engage in the wholesale and wanton slaughter of civilian populations using any weapon of mass destruction. The actual language of the edict is clearly oriented towards nuclear or kinetic strikes, but it applies more to the intent and purpose of the weapon than to its actual characteristics, except inasmuch as those characteristics may define the controlability of its area of effect.
Under existing interstellar law, the phrase "wholesale and wanton slaughter" has a very specific meaning.
"Wholesale" means civilian casualties which go beyond the collateral damage associated with legitimate military operations as defined under the "laws of war" applicable to the Honorverse. "Wanton" means that those casualties were inflicted deliberately, or that prudent precautions to prevent them from happening were not taken. The Eridani Edict does not prohibit the use of "weapons of mass destruction" against inhabited planets. What it does do is to establish the parameters under which those weapons may be used.
First, they may only be used by an attacker who controls near-planet space. That is, a raiding squadron which dashes in, passes within weapons range of the planet, and then lopes off again before a relief force can turn up and kick its butt, cannot pop off a few missiles at the planet as it passes without violating the Edict. Before it can fire at targets on the planetary surface, it must have established that the planet has no immediate prospect of relief, and that they (the attackers) are in a position to send down assault forces if they choose to do so. At that point, the attackers are entitled to summon the planet to surrender upon pain of bombardment from space. If the defenders choose not to surrender, then the attackers are justified in using bombardment to take out specific military targets rather than sending their assault forces down to be slaughtered trying to take them with infantry or armored units in an effort to prevent civilian casualties.
The military targets which are legitimate candidates for bombardment are also clearly understood to fall into specifically limited categories. They may be command-and-control nodes, such as planetary military and/or political command structures and facilities. They may be tactical weapons positions or troop concentrations. They may be civilian communications facilities which have military applications. However, all of them must have immediate, tactical applications and capabilities.
What this means is that a planetary defense missile battery, wherever located, is a legitimate target. The defenders can't stick the missiles in the middle of Central Park in New York City in order to protect them against attack under the terms of the Eridani Edict. If there are weapons there, then they are legitimate targets for attack. By the same token, if two armored divisions dig in to defend New York City and their commander refuses to surrender, then they become a legitimate target. The White House in Washington, DC, would be a legitimate target, as would the Pentagon, because of their command-and-control functions. A civilian powerplant being used to provide electricity to weapons systems, or sensors, or electronic warfare platforms, would also be a legitimate target. However, a factory which produced missiles but had no capacity to fire them, would not be a legitimate target because it poses no immediate tactical threat to the fleet in orbit around the planet or to the assault troops which it might land to take possession of the factory. Similarly, an orbital bombardment attack on the basic economic or industrial infrastructure of the planet would not be justifiable under the terms of the Edict, nor would a "demonstration strike" on a population center intended to terrify the rest of the planetary population into submission.
Note that to a very great extent, the exact nature of the weapon used is not really relevant. Certain weapons, because of the impossibility of reliably limiting their areas of effect, are more likely to be considered a violation of the Edict, of course. A neurotoxin used against a specific, legitimate target (like, say, a palace where the enemy star nation's monarch and top military commander might be hanging out), would not be considered a violation of the Edict unless it was likely to spread throughout a surrounding city, or something of the sort, and inflict truly massive casualties. The use of a biological weapon -- say, anthrax or the Ebola virus -- very probably would be considered a violation of the Edict because it would probably spread far beyond the immediate, legitimate military target to the civilian population at large. Put another way, a biological or chemical weapon [attack] on the White House which took out everything between M Street to the north, Marine Avenue to the south, the Potomac River Freeway to the west, and 9th Street to the east, would not constitute a violation of the Eridani Edict, but the use of a weapon which spread beyond that area to the city at large, and possibly beyond that to Baltimore, Fredericksburg, etc., would.
The "wanton" portion of the Edict's prohibition is intended to prevent people from saying "Oops!" after "accidentally" inflicting damage the Edict would otherwise have prevented. The Edict requires the attacker to take precautions to prevent "accidents," and assumes that if such an "accident" occurs anyway, then adequate precautions were not taken. In that case, the attacker assumes the guilt of having carried out the attack deliberately, and the Edict goes into effect. Which means that even if the attacker controls near-planet space, and has summoned the planet to surrender (exactly as required by the Edict), and elected to bombard specific, legitimate military targets, he had better make damned sure that his "legitimate" bombardment doesn't get out of hand and inflict additional civilian megadeaths. This is one reason everyone keeps sweating the use of MDMs around inhabited planets. If you screw up and hit a major population center on a populated planet, even accidentally, with a notoriously inaccurate "weapon of mass destruction," then you haven't taken "prudent precautions," and you, my friend, are in violation of the Edict.
Genocidal vengeance strikes always come under the heading of "wholesale and wanton" destruction of life, as far as the Eridani Edict is concerned. The Eridani Edict doesn't say that the total civilian population of a planet whose government and/or military has violated the Edict will be killed. It says that the political leadership which authorized the attack, and the military forces which carried out the attack, will be held accountable, and will be executed. A government which authorizes such an attack will be destroyed as a government -- after the execution of the specific politicians involved -- and replaced with something else. A military which carries out such an attack will be disbanded as a military -- after the execution of the military personnel who ordered and carried out the attack -- and may at some distant point in the future be replaced with something else. However, from a moral perspective, the Eridani Edict can't justify wiping out an entire civilian population, the vast majority of whom presumably had no direct part in the attack being punished, because that population's government violated the Edict.
Now, if the planetary government and its military refuse to surrender once the fleet there to implement the Eridani Edict has control of near-planet space, then that fleet is justified -- under the Edict -- in doing any of the things already described above. And please note that any command-and-control node of the violator government and/or military is a "legitimate" military target. So, to continue to use the US example, if the United States government had been guilty of a violation of the Eridani Edict and refused to surrender, Washington, DC, would clearly be a legitimate military target. If Washington were destroyed, and the US government moved to Chicago, continued to exercise its control functions from that city, and continued to refuse to surrender, then Chicago would become a legitimate military target. And this would continue to be true as long as a recognized US government continued to exist and to exert control over the territory of the United States. The theory (which would almost certainly prove accurate) is that by the time the attackers got around to taking out, say, Evanston, Indiana, as a "legitimate military target" because it had become the seat of government, the surviving population of the United States would cease taking orders from the lunatics refusing to surrender and start breaking out the white flags. At which point it would probably be up to that same surviving population to apprehend any surviving members of the government responsible for the Edict violation and turn them over. (Assuming that any of them remained unlynched by their fellow countrymen.)
The reason I've gone to such lengths to explain the Edict is that I suspect from what I've already said that it ought to be painfully obvious that a retaliatory strike of the sort described above against a planet could never be justified under the terms of the Edict. It's probably worthwhile to get this fuller and more complete discussion of the Edict out, anyway, of course.
I know that there's been some discussion about what would happen to the Edict if the Solarian League, its traditional enforcer, were to come unglued and disintegrate. Obviously, no one can know at this point what would happen (tum, te, tum, te, tum), but it would seem likely that this particular "law of warfare" is so vital to the survival of civilization in a universe equipped with the weapons available to the Honorverse that someone would have to emerge to enforce it, even if that required a mutual agreement between warring star nations. Otherwise, an interstellar Dark Age would almost certainly be in the cards, wouldn't it?