After a few days of trying to organize my thoughts, here's what more I have to offer. It admittedly gets a bit speculative in places as it goes on, though I think still with a reasonable basis in what we've been shown, so I'll start with some responses to specific points other posters have made in the meantime...
It seems likely that there are no more separate UFP member militaries in the 24th century-- or at least not with a significant combat strength - otherwise I can't see how these would have escaped any mention as a significant factor in that protracted Dominion War, for example (I only can recall those localized Betazed defences that were considered obsolete).
Well, just because Betazed had pitiful defenses doesn't necessarily mean everyone else did as well. I mean, the Betazoids seem to be a particularly open and easygoing culture, don't they, what with all the touchy-feely empathic stuff and such? And Earth also had its Mars Defense Perimeter, which was certainly woefully undermatched to a Borg cube, but then so seemed even the armadas of starships that we saw go up against them, but for our
Enterprise-ing heroes swooping in to save the day at the eleventh hour.
Sounds like "Military" is a rival fighting organization to "Starfleet", just like "US Army" is the rival of "US Navy" today. Sure would be discomforting for Army Rangers to board a Navy vessel, as if Navy SEALs couldn't do their job!
This covers all the four references to "the Military" in Star Trek, really. The ENT heroes concern themselves with pure interservices rivalry; Picard disparages the Military for its mindless drills that professional Starfleet fighting men and women don't require; and Scotty similarly thinks he's being asked to do the sort of mindless obeying that the infantry in the Military is infamous for.
I see what you've hit on there with "the Military" (as in "the Military Assault Command and its Operations" I take it), but then we have numerous instances within the same period and beyond of it being used in the general sense familiar to us today. Malcolm repeatedly describes himself as coming from "a military family" in context of the Royal Navy (which interestingly apparently still exists in some form). David Marcus says "scientists have always been pawns of the military" in context of Starfleet itself, as does Sisko in "Paradise Lost" when he calls Leyton's plan to put Starfleet in direct control of the government one of "military dictatorship." There are no doubt others that escape my mind at the moment. And neither Scotty nor Picard uses it as a proper noun with a definite article anyway. Commendation for original thinking, though!
Older guns having stun settings does go against the spirit of the "Broken Bow" dialogue.
Honestly, I can't see how it does. That the EM-33s had no stun setting of any sort seems to me a
huge leap to take from the dialogue as presented, and I do not for a moment believe that was its intent. I say this again now after having reviewed the actual scene rather than going by the transcript alone. There is
nothing about it that attributes a sense of novelty to the presence of a stun setting
itself, merely to the overall design of the weapon. And how can you say
this goes against the "spirit" of the text in the same breath that you suggest interpretations of the "military" comments that go much
more against their own likely intended meanings?
(For the record, I'm not one who believes that authorial intent should always be taken as the ultimate arbiter in explication and interpretation of a text, and I very much enjoy many of your posts on various subjects for their boldness and imagination in going beyond and even sometimes against it. I just don't see
this as a remotely logical inference to draw from "Broken Bow," irrespective of whatever implications it might or might not have in any point of view on the debate as to Starfleet's nature.)
Every Starfleet phaser and alien weapon with a stun setting has been configured in the same manner
I really have no idea where you are getting that from.
I don't get the "left must be stun" argument, as there's absolutely no hint of standardization in phaser controls through the ages. But I want to point out that the distinct MACO guns, supposedly trusted old plasma blasters rather than 'em newfangled phase guns (compare the visual effects), still had the ability to stun, on two S3 occasions.
So soldiers armed to the teeth boarded the ship? Well, they met other soldiers armed to the teeth (and with better guns), in Starfleet uniforms
To be fair, while true about the VFX, it's also stated that the tactics and technology of the MACOs are two or three years
ahead of Starfleet's in "Harbinger," despite their expertise arsing exclusively from simulated combat conducted on Earth. (The latter caveat may have some bearing on other points I will go on to make.)
Actually, only military organizations are permitted to arm ships these days. For example, in Canada, the Coast Guard is a civilian agency, and it's ships and personnel are not armed. With the exception of the ships sent to the North Pole, they are allowed one rifle, and it's only to be used against polar bears.
We are not talking about the situation "these days" though, but one more than a century from now, after protracted global war the likes of which we have never yet seen has ravaged the planet and destroyed most major cities and governments—thus throwing all the negotiated international conventions that govern these matters today out the proverbial window—and contact with advanced extraterrestrials has led to humanity's reunification under a new world government that might well make some different choices from its predecessors, perhaps especially under the pointedly (

) guarded stewardship of said advanced extraterrestrials. (More on this coming later.)
If your argument is simply that any armed organization working in any capacity and for any purpose on behalf of a government constitutes a military force, irrespective of how it defines itself, then of course Starfleet meets those criteria and I must concede. But I think that definition too broad given the circumstances of the time period in question and the terms in which our characters are heard to describe them. (And even at present, the FBI/CIA/DSS could be seen as meeting these criteria, and they are civilian organizations that work in conjunction with the military and its objectives without being themselves part of it. Not that I am necessarily arguing Starfleet serves the same roles they do—indeed, there is is probably
no present-day earthbound organization that would yield a truly adequate analogue to Starfleet—but it's worth pointing out.)
Rifles to fend off polar bears is exactly what I had in mind with my "Alaskan wilderness" comment, but when dealing with exploration on the scale at hand, into vast space already known by the time of NX-01's initial embarkation from Earth to contain a myriad of dangers that go far above and beyond predatory animals, including hostile aliens with advanced ships and weaponry, the degree of armament necessary to maintain the same level of protection must accordingly be greatly extended. I don't see why plasma cannons and spatial torpedoes need be taken as transcending what might be deemed essential for self-defense in the exploration of such an environment.
And Archer's ship had big guns, whereas we never heard of a MACO ship let alone one with big guns.
ENT makes much noise about NX-01 being the first exploration vessel of any worth in the UE Starfleet... In contrast, nothing is said about preceding combat vessels, for or against. And we indeed see that preceding vessels do exist, and have major combat capabilities.
I cannot recall even a single example of a Starfleet vessel that we can conclusively say
both precedes in its construction
and exceeds in its firepower and tactical capabilities NX-01—a vessel quite explicitly designed for the purpose of exploration, as you say—let alone one whose intended purpose was combat.
Unless there's something I'm overlooking, the
only military conflict remotely involving Earth that we have mention of between the end of World War III and Starfleet's founding (presumably in the 2130s) are the "four wars" fought between "humankind" and the Kzinti in the late 21st century, according to "The Slaver Weapon" (TAS). We can't say much about them in terms of their scale, location, or duration—except that they must have occurred between 2063 (to preserve "first contact" for Earth; and we should probably even say 2067, when
Friendship One was launched with us still having "no idea what was out there" in terms of aggressors) and let's say roughly 2075 (Sulu said the last of them ended "two hundred years" prior to 2269-70, which I think can be readily fudged a bit given how round a figure it is)—but they all ended in victory for the human side, seemingly resulting in the Treaty of Sirius, which forbade the Kzinti "any weapons at all beyond police vessels."
Since these conflicts clearly occurred after contact with the Vulcans, could it be that they had a role in brokering the peace—after all, despite their victory, humans would scarcely be in a position to enforce such a treaty when they'd only barely begun to leave their solar system to found colonies such as Terra Nova and Terra 10—and that not only the Kzinti side came away with restrictions imposed on it? Is it possible that, while quite evidently not being so extreme as to forbid all armaments as it did to the feline losers, the agreement disallowed Earth from having a standing space force that was explicitly military in nature, similarly to Japan after the World War II? Perhaps this is why, prior to tagging along with Archer, the Military Assault Command was restricted to Earth (which was free of war by the first decade of the 22nd century according to
First Contact, thus explaining their combat experience being limited to simulations as aforementioned), and why Starfleet could only be founded as a nominally exploratory force under the aegis of the civilian-sounding United Earth Space Probe Agency, and armed ostensibly only for self-defense?
Now, all that being said, when I suggested some posts back that the process of Starfleet's inevitable militarization had "only just begun at the time of ENT's third season" this was probably an overstatement, because I'm sure that it could actually have been going on behind the scenes
at some level and
to some extent from its beginning. (I think when I put it that way I was thinking in terms of the bigger picture of where things would go beyond there, in Kirk's time and in Picard's.)
There will always be humans who wish more than anything to explore, and those who wish more than anything to remain secure, and even those who wish more than anything to make war. (The latter might be exemplified most stereotypically by Admiral Marcus in
Into Darkness.) It's likely that just as they would constitute its ranks, examples of
all three may well have played a role in influencing Starfleet's conception and development both before and after its founding, including the design of its vessels. There were probably those who foresaw more than others as to the eventual need for Starfleet to act as a military force. Section 31 is clear evidence of this.
In substantial part, in ENT our window onto this process is Jonathan Archer, and we see it unfolding largely through his eyes. He starts off as a wide-eyed explorer, who resents the Vulcans for "holding back" humanity (and in particular his father) and longs to penetrate the reaches of the unknown—yeah, man, very Freudian—but in the course of his explorations finds this unknown to be more full of threats than he or his planet are prepared to handle. Ultimately confronted with this in the form of the 9/11-esque Xindi attack on Earth, he becomes an advocate for integrating military concerns and operations with Starfleet's mission, and beyond that further he comes to see the pivotal value his organization has as an instrument of diplomacy in the formation of alliances among former rivals for mutual protection and benefit. Again, he surely could not have been the first to travel this path, but it's a journey we as viewers take with him through the show.
To bring this all back around to the main thread topic, Cochrane's achievement of warp flight coming at the particular moment it "happened" to was of
paramount importance—no pun intended—in this
all unfolding the way it did, as a pebble dropped into water creates propagating ripples, or dominoes fall one upon another, and thus is an event hugely significant not only to human history, but to the
entire future depicted throughout the
Star Trek mythos.
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MMoM