The use of battleships is....questionable..in any potential fleet engagement but they're obviously as scary as heck in a raiding environment.
Obviously, the PRH does have major structural problems. Pre-Rob Pierre (and more importantly Pre-Oscar Saint-Just) they've got massive social instability but the potential rebels are a lot less cowed prior to the reign of terror; using those battleships is possible but the risk is big - that doesn't mean they wouldn't but the risk has to deliver big.
I didn't say a direct strike had to come off the table, just that you needed a pretty decent plan at the time to make it feasible. Honestly, I think it is the best plan, but it needs a more fleshed-out concept than "
we take the entire PN battle fleet and throw them at a head-on assault on Manticore."
Certainly, between the cabinet essentially giving the go-ahead for 'stuff' (which was Odysseus, Jericho, and whatever else might have happened 'off-camera') and actually pulling the trigger on open war was something like
five years, and it's fair to say (the cabinet even observes) that during those five years the force balance gets steadily worse because Manticore and Grayson build better ships and do so faster.
Did Haven have a significant enough advantage in ships to offset the RMN's tech and seriously threaten Manticore then?
in 1904 (post Basilisk and Grayson but pre-Hancock), the PN had 460 dreadnoughts and superdreadnoughts to the RMN's 309. Based on Amos Parnell's estimate of the RMN units having a '30% edge', that puts the RMN at an equivalent of about 400 "PN capital ship equivalents" to the PN's 460.
More importantly, that's with the RMN's armament programme running as fast as it can with Cromarty hoofing the exchequer in the painful bits at every opportunity for more funding; every year you wind back puts the balance more in favour of the PN. Plus, if you set your plan's 'zero hour' date further back towards 1900/1901 you're getting the drop before the RMN gets deployable missile pods into general service, and potentially even before FTL beacons are freely available.
On the other hand, you lose access to the Argus sensor platforms, although to be fair the systems they are watching aren't part of the manticoran alliance prior to that point either.
Essentially, if you could put the entire PN and entire RMN in a single volume of space and compel them to fight, the PN should have won. The trouble is coming up with a way of compelling that to happen in a way that doesn't let the RMN just disengage, and doesn't feel like you're taking the entire PN battle fleet and flipping a coin to see if it survives.
The problem is that the obvious centre of gravity to attack is either Manticore or the Manticore Junction, and whilst the numbers above ignore the PN's battleships (because they're pretty much nailed where they are aside from emergencies) it also ignores the junction forts and other system defences such as LACs and fixed missile emplacements, which are a huge military asset when considering Manticore's system defence.
That said in turn: based on Honour Among Enemies, we know 31 fortresses is "a quarter of the entire Junction Defence Force" and that 50 PN battleships (admittedly with the benefit of surprise in presumably energy weapon engagements) were able to kill that many before being wiped out, presumably by the concentrated fire of the full 120-odd fortresses.
Munroburton is right that defeat in detail is critical.
You need to bring the PNs numbers to bear against targets the RMN can't ignore (note that if you're not planning on Epsilon Eridani violations I'm not sure planets other than Manticore itself necessarily count because there are limits to what you can achieve if you can't take either the shipyards or Mount Royal and the Admiralty), and you also have to get around the problem of the PN's logistical 'tail' - extended fighting around Manticore automatically favours Manticore (obviously) but doubly so because Haven was designed for short, high intensity campaigns with relatively small sustained missile reserves per throw weight and relatively little organic repair capability compared to Manticoran units.
Ultimately, I suspect the smartest thing to do is (1) accept you're the bad guy and (2) do what was originally planned as part of Odysseus at that point in time; roll up a battle squadron or two, park it on the Basilisk terminus and mine the heck out of it. There's no way you can credibly stop a warning getting out (one assumes that when you had got multiple ships there pre-On Basilisk Station at least one would be at the terminus, but against an incoming superdreadnought formation all a cruiser can do is dive into the terminus screaming 'ZULUZULUZULUZULU'), and equally there's very little chance of a Manticoran fleet making it through in time to stop you; the forts aren't wormhole-capable and the hyper-capable units are too far away to arrive with heavy enough units in a short enough time.
Unless you're prepared to invest a huge chunk of the PN, you can't stop the RMN taking the system back, but you can make any attempt unbelievably bloody, because a wormhole transit into a weapons-free minefield is exactly what the RMN wanted to inflict on the PN but the other way around.
Ultimately, the 'checkmate' position is the PN in control of the Manticore junction and Fortress command destroyed without the PN losing catastrophic numbers of ships (or at least with the RMN taking equivalent warship casualties so the PN's available forces remain better). Manage that, and you essentially have Trevor's Star and all the logistics and PN reinforcements you need available in the Manticore System, meaning the whole thing is essentially reduced to a single-system problem of a big fleet against a bigger fleet, and that's a battle Haven had fought and won time and again.
What I'm less sure is
how you get there.
