What do we know so far? Well the previous duke died in 4998 so that's the earliest point at which the war began. Given that the information in the GM's guide is dated at 5002 that means up to five years of conflict during which 25,000 people have died so far.
The planetary map of Ravenna seems to indicate that the front line of the war is the stretch of sea between the two islands.
The eastern island (supported by the our murdered Baron in our current storyline) is run by Countess Cassandra Justinian Hawkwood (possibly a relation of both our Player Character Hawkwood and Justinian). She is an artist and scientist, not a military leader and lacks both Orthodox Church support and is the poorer of the two islands. While her people are generally very loyal, her greatest external support comes from the Trusnikrons of Follari (so perhaps she might field beast based cavalry such as Urroc airborne knights and "beast master" units). It's noted that there is a naval base on the northern coast of and that her island is also the location of a Deep Core city run by the Muster Guild. Therefore she may have access to not only a wet navy but also Guild mercenaries (but the coffers may not support them for long, unless there is some sort of "non-financial" deal worked out). While the Orthodoxy doesn't favour the Countess the healers sect, Sanctuary Aeon have interests on the island after supporting and assisting in the various natural disasters in recent years.
On the other hand the Western island is ruled by Count Otto - a veteran of the Emperor war and outspoken military strategist. The island can rely on better financial wealth and a wider base of support outside of the islands themselves. Due to his outspoken piety (and significant investment in local church buildings...) the Count has the support of the local Orthodoxy and it is very possible that they may mobilize forces in support of him, and his claim of sovereignty.
So, what form does this war take? The map suggests a naval conflict but the death toll seems almost two high. Given average naval crews (based on World War one battleships, which I figure is about the right tech level); destroyers had crews <100 with cruisers in the 2-300 range. Ships of that era were rarely lost with all hands which means hitting the 25K death toll seems hard especially as I can't see that either island would be able to maintain the loss of that many vessels (and manpower) financially, especially as the islands still seem to maintain some form of order, there've not been completely militarized and turned to the war effort (there's mention of the forests of the West and noble hunting parties along with the land reforms and public opinion in the East. However could that go to explain why it's become such a protracted conflict? They two islands are in a slow and drawn out war of attrition? But then how come there's such a "senseless" high body count?
One idea I had could be that the front line on the map is actually two fronts; troops have landed and established beachheads on each of the opposite shores, with the ocean between them a watery no man's land of sorties, patrols and skirmish encounters. The issue then would be supply lines for the entrenched beach heads (which has echoes of Gallipoli campaign in WW1).
Anyhow I'd appreciate any thoughts on making sense of any of that rambling.
(digressed from writing my "sample player's fief"...) so expect "something" soon.