The Terran Trans-Solar Federation
The T.T.F has the unique position as humanity's only superpower. The wealth, power, and relative peace within its core systems are a boon for the vast majority of its citizens. They enjoy a level of freedom and independence unknown to people on Earth before the space diaspora. Taxes and federal laws are more strictly enforced. Yet most people are happy to sacrifice some of the freedom the outer colonists enjoy for the added level of security and support, especially against exterior threats like pirates, terrorists, and Avarians.
Earthlings are happy to enjoy world peace, especially with such an incredible overcrowding problem. When thousands of Earthlings emigrate to other star systems they hope to find new homes in Terran-friendly colonies. For those still identifying themselves with Earth, the Terran Federation is the only government for them.
For the Delta Sector, the Gamma Sector, and elements of other outer regions, the T.T.F is the old tyrant they finally escaped. Despite family ties and friendships with loyal Federalists, most independent colonials despise the Federation, uniting their fledgling nations under banners of opposition. The loss of hegemony on humanity's frontier is a serious regret for the Federation and especially the Navy, but the real threat is in the Avarian United Worlds. In the face of this threat, not only is national prestige at stake, but so is humanity's hope of challenging alien aggression before humanity itself is enslaved by the bird race. To combat this the T.T.F has the resources of more than a hundred worlds at its disposal. Its navy patrols and protects 28 different star systems with almost two hundred space stations, civilian and military.
The Terran Trans-Solar Federation Navy
The Federation Navy is by far the largest military force ever mustered in human history. More than 70% of the human warships in space belong to the T.T.FN. Below is the breakdown of ships available.
Terran Navy ships are versatile. An individual Terran warship can sometimes be bested by one of their enemy's equivalent ships, but the Navy's ships will be able to overwhelm the opposition in short order with its numbers. All the while, it continues to defend its other borders.
The Federation controls little real estate on planets; and has few non-military space stations. It guards these jealously, and constantly lobbies parliament for more permanent holdings.
Only 200,000 people live in areas directly owned by the Federation. The pool of new soldiers, spacers, and bureaucrats, must mostly draw from colonial and Earth recruits. To entice a better class of candidates, the Federation offers knighthood to all spacers who complete at least three full tours of duty, or 10 combat missions.
This is a quasi-aristocracy. Children inherit a lot of prestige and the privilege of class. They are not granted full knighthood status until they have served the three tours. But they commonly get assigned the best duties, so success is not that difficult.
Certain families have commanded specific fleets for generations. Unlike a true caste system, the "Federal Formula," as it is called, blends this with merit-based advancement of even the lowest ranks, enlisted officer training, etc.. It's far from egalitarian, but a truly talented spacer of even the lowest ranks has at least an even chance of making it to the rank of captain. The captain's daughters and sons can begin their careers with a leg up. Several of the top admirals are grandchildren of fleet auxiliary deck hands.
Just as historical feudalism, the galactic knights have developed their own code of chivalry, governing honoring cease fires, POW exchanges, surrenders, and other rules of engagement. Nova Liberia and several other independent navies.
source: Terran & Avarian Fleet Book