Basileia Rhomaion

Also known as Eastern Roman Empire and Byzantine Empire, and also one of the most succesful cases of countries created as historical reenactments. Byzantine Empire was created by a group of wealthy people fascinated with the Byzantine Empire as it existed in history before it's ultimated fall at the hands of Turks.
Or, to be exact, a recreation of Byzantine Empire as seen by said group of wealthy people, since many elements are changed (or 'improved') to better fit the reality of the space empire. It also underwent certain changes due to Neocatholic Church influences - why it hasn't defected to Paleocatholic Church is anyone's guess.

Structure

Basileia Rhomaion is essentially a hereditary (to a point) military dictatorship. Absolute ruler of the empire is titled Basileios and his position is at least partially despotic as he is pictured as a sort of God's right hand, governing the Empire in His stead. The Basileia Rhomaion didn't lose track of its origin, so the Basileios position lacks the semi-oriental grandeur and complicated etiquette of the late terran Byzantine Empire.
The situation does fluctuate. The history of Basileia Rhomaion can be divided into three periods that keep repeating themselves over and over again. Firstly there is a period of relative stability and power under a system of 'military' emperors, with ruling basileios electing 'ceasars' from especially succesful military commanders to serve as their designate heirs. Then there are periods when the Empire is truly hereditary, which always corresponds with period of internal weakening of the State, as later emperors keep having less and less authority (with personal authority being one of the main sources of their powers). And, finally, there are periods with unrest and a de facto civil wars, with sometimes several succesive succesful usurpers, that ends when the country is tired with the strife and/or one of the emperors is strong enough to push the Empire into either hereditary monarchy or a succesive military dictatorship periods.
Beneath the authority of the basileios there exists an imperial government... however, due to how big is the territory they have to govern, it is actually limited in power. Most of the power lies in provincial governments (mostly including an inhabited world and several nearby star systems), governed by governors elected from the imperial court (or a senate, as it is often called). This is the civilian side of government. There is also military one, in the form of themes, military 'provinces' that tend to exist in parallel to civilian provinces.
This system manages to at least partially weaken chances of succesful usurpations. Most wannabe basileios comes from the strategos ruling over theme. However, they only control a detachment of warships and the on-board marine units. Even taking over the province of their origin can be troublesome, since ground defense (including entire armies, both of regular soldiers and conscripts) are under control of the province governors. What's more, the ruling basileos not only control the elite formations of the byzantine army (including a significant part of its mechanized and tank elements) but also the dreaded Varangian Guard, composed of Voca aliens whose loyalty to the Empire is well known. It requires the empire to be in serious crisis for the strategos to gain enough power to overwhelm the ruling government.

Public Agenda

Basileia Rhomaion is one of major superpowers of the Res Publica Christiana. It's main agenda is for the situation to stay that way while expanding the Empire's influence throughout nearby star sectors. The chances for it to conquer them are nil (due to logistic troubles and the hyperlane's being heavily fortified), but even having significant influence is enough.

History

Basileia Rhomaion began as one of many 'historical reenactments' in the forms of colonies. Created by a group of wealthy people (mostly from Greece, but there were also many from Russia and several other countries, connected with bonds of the Eastern Orthodoxy faith) fascinated with the Byzantine Empire. It existed like that for many years, slowly growing stronger and losing the 'historical reenactment' trait - as in most cases of such cultures, the part about pretending got dropped in second or third generation, as the descendants of the founders genuinely obeyed the tenets of the culture they were born into.
When the Unification Wars started, the whole sector quickly fell into chaos as local Federation Navy headquarters were orbital bombarded by a democratic corsairs fleet. Some of the surviving ships ended up defecting to the Byzantine Empire, due to its leadership investing a lot into orbital infrastructure that could sustain them... and build more warships.
The Empire won the contest for being the first country to start producing military ships of at least some level of combat ability, even without access to any pre-Unification War Federation shipyards, since none of them were in the sector. What's more, the Empire had no moral qualms about ensuring its own safety by a preventative attacks, annexing several nearby planets after the chaos started.
It was mostly overlooked due to several genocidal regimes rising up in the sector. With the more centrist governments finding themselves being heavily outnumbered in face of several groups of insane maniacs (including one group that was downright omnicidal), the only power capable of standing up to those threat were the Basileia Rhomaion. Surviving democracies and monarchies (plus more tamed of the dictatorships) quite quickly banded up behind it, ultimately ending up annexed though in peaceful way. Most of those countries retained the privileges received from the emperors during their annexiation proccess, being culturally different (and having some degree of autonomy) to this day.
The enemies of Empire that it conquered during the Unification Wars had less luck. Now they form the majority of the mainline byzantine provinces. They were defeated, and their inhabitants mindsculpted into byzantines, with last of them falling before the Unification Wars period ended.
The only difference was the Thanatocracy, said omnicidal maniacs, who were (due to reasons the Empire never announced) wiped out ot the last. With their coreworlds practically sterilized by orbital bombardment. Ever since that, the Basileia Rhomaion continues ruling over the entire sector, remaining one of the main powers of the Res Publica Christiana.

Demography and Population

45% baseline homo sapiens, 35% of Variants, and 20% of various domesticated aliens (5% of them is Voca, the rest varies). Racism is practically non-existent, due to complete equality between various species (up to the point of several basileios being aliens) but also due to Neocatholic Church teachings being widespread.

Military

Ground Forces

Due to having control over entire star sector, the Byzantine Empire isn't forced to maintain a massive regular army at all times to defend itself from unexpected assaults and attempted blitzkriegs. Because of that, for most of the time its army is limited to officer staff. That, in times of crisis, are bolstered with conscripts.
There exists a core of better quality soldiers, that - in case of sudden crises - are tasked with holding the threat at bay before the conscript armies organize themselves. It can be summed up to Imperial Guard - a regular formation of elite soldiers that serve as majority of Empire's tank and mechanized units - and Varangian Guard. That is recruited from local Voca population according to treaty signed when they were allowed to settle in the Empire. If Imperial Guard is the basileios hammer, then Varangian Guard is his dagger. Each of its soldier is an elite, and their very elastic doctrine allows the imperial commanders to use them as special task force, defending and attacking key positions at a moment's notice.

Navy

Divided into themes that also work as a region-bound fleets, then divided into squadrons and so on. Good ships, rather typical artillery-focused tactics, with at least some focus on maneuver. It's biggest problem is general lack of experience due to relative peace in which the Empire remains pretty much since its inception (civil wars are mostly brief usurpation attempts that pit their officers against other officers using similar tactical doctrine).
It also has a negative side effect of having their shipyards focus a lot on aesthetic beauty of their warships due to their expected service time being rather long and battle casualties being limited. On the other hand, when the Emperor decides to participate in another neocrusade, he in most cases sends enough forces for the quantity to fix the quality problems.

Technological Level

Due to technological exchange with Voca, the Byzantine Empire is believed to be the most advanced country of the Human Space in terms of Alcubierre Drives and Engines. While they can't be used to move their ships around, they have certain usages in terms of sending almost undetectable scout probes into enemy systems.

Religion

99,9% of the population remains a part of the Neocatholic Church. 4/5 according to Eastern Orthodoxy rites, while the rest is mostly Greek Catholic. The remaining 0,1% includes Varangian Guard soldiers (Voca aliens, hailing from a radically different culture) and few immigrants.

Basileia Rhomaion

O Stavros Nika!

Capital: Blachernae Spire on New Constantinople
Official Languages: Greek
Religion: Eastern Orthodoxy variant of Neocatholicism
Government: Hereditary Monarchy/Military Dictatorship
Faction: Res Publica Christiana
Membership: Standard/Secondary Power
Current ruler: Emperor Constantine XXV
Population: Approx. 34 000 000 000.
Currency: Solidus

Alternative Names

Byzantine Empire, Eastern Roman Empire, Romania.

Demonym

Byzantines, Eastern Romans, Graeco-Romans.