Regarding Last Throw, I think "final strike, after which there will be no hostilities" is indispensable to the concept of Societist war, but the definition of the term will likely shift over time and especially after the nuclear bomb. I mean, if A and B are hostile and A destroys B's capital, then that will be the "last" attack since B can no longer wage war (or so the Combine will assume, until Russia shrugs off the loss of Moscow). So after carytic physics reaches a certain level of sophistication "Last Throws" just become a lot more practical.
There's also the fact that in a Last Throw conflict the Societists are theoretically always a third party. The whole principle is that nationalism inevitably creates conflict, so wait for intra-nationalist conflict to weaken them all and then mop up. But as the ASN and Diversitarianism point the way toward a world order that's diverse and peaceful, at that point the Societists go from intervening in ongoing conflicts to sparking new ones themselves. The final leg of that evolution might well be preemptive strikes, as hardliners present a hostile, tenuous peace as being war/aggression by other means ("Peace is war. War is wrong. Peace is wrong.") that must be ended by a final strike, after which there will be no hostilities. So that may be what "Last Throw" comes to signify: ending a conflict by any means even if the Societists started it.
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Besides that, it just hit me how weird it is that "frontiersman" is still a valid political category in early 1900s America. That's what Panimaha is, a collection of every "open range" from Hudson Bay to the Mojave. And even if that territory shifts in identity there'll still be Westernesse and Cygnia. There's still lands in America that don't fit into normal archetypes of city, county, and state, and there's politicians and parties that identify with their interests and pledge to address their unique concerns. And the identity isn't on its way out yet, people are still aspiring to stake claims on this or that even if the enthusiasm isn't enough for Tayloe's plans.