Well I have a huge Roman-style Empire in one part of my homebrew campaign world (in fact they ARE, or were Romans, started by Romans from a parallel Earth, not ours, my settings got a lot of links to parallel or counter Earths).
They've advanced over centuries and have a very affluent culture where politics is not about murder! More like oh mix of Rome with a dash of 15th century Venice and any culture they liked to pinch bits from
The Empire is truly enormous though, and it's borders and other areas are very dangerous.
Rather than "points of light" it's more liek a "web of civilization with bloody dangerous bits in between the strands" and it's a constant battle to keep the strands from being severed.
Large part of it's to do with usign adventurers (hence they are a recognized feature and have guilds) and a very organized police/security force counterign all kinds of schemes infiltrations etc, and the Adamantine Legions who slaughter anything that threatens their homeland.
The legions are armed/armoured in adamantine, which being so incredibly tough, last for millenia, and the Empire
has lasted for 4 millenia, and slowly amassed that arsenal from it's adamantine mines where condemned priosners are sent (it's a death sentence, the super hard fine dust destroys the lungs).
The legions have their own "magical corp", often they take orphans or youngsters whoing potential and train them in magicla arts, in turn they serve minimum of 25 years.
Each century has between 5 and 10 spell casters roughly 2/3rds or so of which are clerics of war. A century is roughly, varying on makeup, 50 infantry, 10 archers/slingers, 10 cavalry, 5 scouts, 5 casters (or up to 10 if they are lucky/hard campaign), and 20"auxilliaries" (who're actually mostly craftsmen, drovers, cooks, physicians and the like and are either retired/wounded ex-legionnaries, experts, or youngsters, they tend ot the necessities and can fight)
Often, elite centuries or a cohort are sent to root out trouble that small mercenary bands (ie adventurers) can't deal with or aren't trusted with (politically).
So it's quite common on the fringes with truly dangerous areas, for a cohort to go in, establish a base, from which adventuring parties or legion scouts hit special targets, and centuries handle larger tasks.
The EMpire has two main military "schools" (that is, not just one establishments each, but widespread learning structures), one teaching battle magic/co-operation with units to casters, the other teaching centurions/officers strategy etc.
As noted, they like getting willing orphans/youngsters and raising them to be very loyal to the legions, which has proven very successful.
A choice between starivng in alleys or worse, and a full belly for an exciting, if dangerous and striclty disciplined life, is one many jump at.
The Legions are a meritocracy and won't stand for idiot leaders, and are very professional, more akin to a modern army in going about it "business fashion". They've been at it 4,000 years so they are definately not stupid, the EMprie cannot afford mistakes, so no "chinless wonders" are allowed
The empire has massive roads and canals across it, plus magical gates for special needs.
That allows comparitivley quick movement of armies. They also have aireal units (dragons hippogriff archers etc)
Generally, they wage total war, that is, compplete extermination, because the foes they face are not by any manner of means safe, or worth keeping aorund. So it's nasty stuff. However, they do eagerly make alliances with those they believe they can use or trust. So on the border, there's friendly or at least,
allied groups of orcs and hobgoblins (there's even a hobgoblin legion who're more neutral than evil, but that legion is usually kept apart from the several dwarven legions to avoid friction).
Often border fortresses get besieged, or they do the same to orcs and undead/drow (the EMpire's worst enemies). Northern orcs use dinosaurs as mounts, southern orcs are often mutated, and worse than them live in the mountains. So it's almost always a constant low gade war.
The Empire is massive and rich enough to field nearly 100 legions and supplies. It doesn't like large mercanry forces, for lot of reasons, but recently has begun using Viking allies in such capacities in the North as both were in trouble and needed each other's assistance. (the Viking folk needed food due to bad harvests and also wanting to develop more trade and advancements, and they needed the security the Empire provided on their sea lanes)
A long time ago the Empire tried taking over an area home to a folk akin to Native North Americans, but they gave that up when they woke up the tarrasque and left that region post haste! A couple of thousand years later, they are sort of allies with those folks but they are pretty remote due ot the difficult terrain and the tarasque prevents major settlements being built in a big chunk of land (hence the locals are semi nomadic, or live in the hills or canyons where the tarrasque rarely if ever shows up)
A massive canyon goes across that land and that's where trade flows along it's river and many odd communities dot it's banks and cliffs.
The worst battles are fougth against the drow and undead from an island to the south. Millenia ago, an emperor was fantastically successful, expanding the EMpire enormously but became a tyrant, to extend his life he became a vampiric lich (rather rare if not unique state, he draws life, not blood to sustian himself). He was eventually driven off, but he still yearns for rule of the Empire.
The drow from this land do not worship Lolth, but other gods and him as their "living god".
They are otherwise every bit as sneaky nasty and deadly as other drow, worse even, because they are seen as heretics.
A recent invasion by that dread emperor, left more than a million dead and the Empire is recovering (hence the use of Viking allies). The invasion was halted and turned back at horrific cost, but it's not over yet and will take years if not two or three decades to retake the captured lands and cities, and much longer to clean up all pockets of enemies.
So you can imagine the horrific battles that raised great cities to the ground, counter epsionage to prevent break outs or mass slaughter of civilians by poison etc to weaken the war effort and so on.
The Empire hires dragons of any type provided they are reliable (dragons only tend towards alignments in my campaign), for various tasks and stations, smelting metal, spellcasters, some enjoy politics and are senators etc.
Dragons are seen as very auspicious (the empire's symbol and good luck charm is a white dragon) and are offered citizenship, provided they stick to the laws like everyone else.
a lot enjoy working for the legions, which treats them as honourary officers, as the dragons can unleash their fury (they really enjoy that), and many of them are patriotic or just plain hate the ex-emperor's blasphemies, and they prove invaluable in battles.
the enemy has dragons too, especially dracoliches (which many living dragons consider abominations), but in much smaller numbers
the vampire lich's homeland is much smaller, comparatively, than the enormous continent the EMpire largely controls, so, less area for dragons, and also, population of humanoids, but the evil ex-emperor makes up for that by massive undead armies.
the undead dont' care about polluting wells and the like, and drow are master of stealth, so the Empire's forces have a heck of a job on their hands...which is why they are so damn professional, they've been through this before and have a "no tolerance" policy of idiocy and break or execute nitwits who play political games that cause harm to the war effort or bad military tactics.
well I hope that's given you some ideas?
