[X] Bear Any Burden
There is never a convenient time to do the right thing.
Of course more options are going to open, but if... if it comes to this
We don't fight the war with soldiers, that's costly and bloody and expensive. We want to fight the war cheap? That's via subterfuge, and economics.
Our spies can dig tunnels all over, liberate our people and we defeat the slaveholders via embarrassment. If we want to step things up work with Ambrosia and set up a network of tunnels to give supplies and underground railways... heh maybe literal ones now, to the north and the freed slaves start new lives north of the Crystal/ Amtheyst/ Beryl/Whatever River. Which solves the problem of a depopulated Crystal protectorate in the long term.
The other way to defeat slaveholding nations? Economics. Find out what the nobles that hire the most slaves do and flood the market with cheap industrial goods and set up railway operations with those plantations. Target the slaveholders, don't go after them... go after their pocketbook. Get Neighpon in on economic warfare and we can win... although they may have other trade partners than Libertalia. The furnace of industry and automation can do it
By the way we might want to build vital infrastructure... like Bridges or tunnels under the Crystal/Amethyst/Beryl/Whatever/Southern Border River so that... if we want to...uh... pay a visit... we can do it easier. Along with the fortresses.