Having introduced two Navy vessels into Aloin’s story, the designs of which are now in the Starships and Space ships page, it seems appropriate to examine the Imperial and Subsector Navies as I see them operating within the RimWorlds.
When Kolin Venuraski (later Sector Duke Kolin I) launched the settlement of the RimWorlds by the 3rd Imperium in the 6th Century, he had at his disposal a small flotilla of Imperial Navy ships for the protection of his colony fleet. This flotilla was augmented by such armed auxiliaries as his supporters could buy, equip, or supply. And as they spread out and were granted, or took, planetary holdings, it soon became imperative for each Noble to possess at least a couple of armed ships to both protect their fief, and to send to serve the Sector Duke when he called for aid. Kolin I took his duties as Sector Duke, and head of his comitatus, very seriously and he did not hesitate to downgrade Houses Major to House Minor status if they did not fully support him.
While numbers of available ships, and the technology level of their build, have fluctuated over the centuries, the current system for the defence of the RimWorlds has changed little from Kolin Venuraski’s day, nor from the House Trumer restoration of the Sector in the 10th Century. There is an Imperial Sector Fleet, currently utilising Tech Level 15 ships, charged with defending the nine Imperial controlled Subsectors of the Sector. Headquartered at the Sector capital Thiroor/Gazolan, Sector Fleet has at least one base in each Imperial Subsector and regularly shifts squadrons between them to maintain a state of readiness. The Reserve Fleet of older, Tech Level 14, units is based at Raelmar/Thurgandarn. There is no mothball fleet as all surplus units are sold to Houses Major to augment their Subsector Fleets.
Each Subsector Duke maintains a Subsector Fleet as his or her comitatus and is responsible for the defence of that subsector, as well as being obliged to commit units to assist the Sector Duke as required. As the standing a House Major holds is dependent upon the resources it can both commit to the defence of its Subsector, and to the defence of the Sector, very few recalcitrant Houses have survived the refusal to render aid. "Send ships or grasp the diadem" is a saying that we might translate as "Do your duty, or take charge", with the implication that the act of taking charge involves irrevocably committing the resources and fortunes of your House to both overthrowing the current Sector Duke and dealing with whatever problem was threatening the Sector.
Houses Major of Siridar-Count and Siridar-Baron rank can, and often do, maintain Planetary Navies which both defend their respective systems, and support their Subsector Duke as required. This ships may be built locally, or purchased from shipyard systems. Even System Defense Boats can be moved from system to system if there is sufficient Jump-capable transports of suitable tonnage available.
On the whole, this system works reasonably well with Subsector Fleets, usually backed up by a Sector Fleet squadron, being sufficient to maintain order or deal with most border incursions, and the heavy units of the Sector Fleet being committed only in the event of a major war.
In Miazan Subsector, the bulk of the 12.1 billion Imperial sophonts are concentrated in just three systems – Nakaya, Exxilon and Miazan.
The 6.2 billion inhabitants of the isolated Nakaya system make do with an average Tech Level of 7 – below Interstellar, meaning that they lack the technology to produce the machines that produce the machines that manufacture starships. While the Siridar-Baron of Nakaya maintains a few orbital forts and a large System Defence Boat flotilla, these have all been purchased from elsewhere and have to be maintained by expensive off-world technicians. Nakaya does contribute approximately one fifth of the annual Miazan Subsector Navy Budget of TCr 5.1.
With a population of 575 million sophonts, the Exxilon system is just on the edge of developing a native starship building industry at Tech Level 9 – or it will be when it develops its starport further. Like Nakaya, its greatest contribution towards the defence of the subsector is to finance shipbuilding elsewhere.
And elsewhere just happens to be the Subsector capital of Miazan. With a Tech Level of 12, an A Class Starport, and a population of 5.2 billion, Miazan has a yard capacity of over 6 million tons and the ability to produce ships of up to 100,000 tons in size. It is also the only major starship producing shipyard facility in Imperial-controlled space within the Subsector.
For the last decade, yard space at Miazan has been at a premium as House Geyukthi, Dukes of Miazan, have sought to replace Navy losses incurred during the 4th Outrim War and the Kalar-Wi War, as well as encourage the expansion of interstellar trade required to boost the subsector, financially. With such a bottleneck in the supply chain, and the smaller shipyards at Celephais out of action due to damage sustained during the Kalar-Wi War, the Miazan Subsector Navy is finding itself being out-built by neighboring polities that it is obliged to defend against.