# How do you make a Roman-esque style army more adaptive to situations even if they've never confronted them?

So in my fantasy world, my Emperor has recently come into control of a declining empire and managed to restore its control over the continent he lives on. This empire, a continuation of previous empires, has had a long history of its armies. This Roman-style army has existed throughout since the founding of the first empire and continued to exist even when the empire was dissolved/fractured.

Now here's the problem; this army while powerful had suffered major losses during the Emperor's war to control the empire. The Emperor can restore the army back to its previous numbers however he wishes to reform the army's organization. This is due to the fact that the empire was on a decline against a rising power and was only able to defeat it due to the Emperor's own powers. Thus he wants to reform the army in a way to where it can deal with any situation that it faces whether it be guerrilla forces, mages, monsters. It can adapt quickly to its confines.

What should the Emperor do to move his force's in this new direction?

Now there are some parameters the Emperor must work in:

• He has 100 years to work with as he plans to invade another continent
• He has no political or social impediments to his changes due to his popularity and his own power
• The most soldiers he can possibly have as a standing army is 400,000
• The max tech level that can be achieved is comparable to 15th century Italy/Germany

These are the current characteristics of the army:

• It is organized in the tactics of the Roman army during the reign of Augustus however there are no slaves
• Weapons and equipment are the same standards during Augustus though infantry don't carry pilum
• Promotion is meritocratic but there is some bias towards nobles
• The gender makeup is 65% men and 35% women
• It is considered honorable and righteous for citizens to join but the pay is about just enough to get by in life
• 5% is made up of mages/ soldiers proficient in weapons and magic

The current organization also as follows:

• The army is organized the same as during Augustus up to a legion and then divided between the 9 regions of the empire; each region has a head General of all the legions in a region
• The regional generals respond to a General of the entire army who in turn responds to the Emperor
• Communications are handled through a magic spell that works like a Star wars communicator; only those from a Legate to the Emperor have access to such a spell either through themselves or from a mage within their units
• Supplies are carried over baggage trains of horse wagons or mages levitating them over rough terrain

And finally to what the Emperor can't do:

• No guns or cannons due to how versatile the magic is
• No full-on mage armies as there are spells that prevent magic from being cast
• He also does not want to copy the organization of the rising power he defeated; it relied heavily on skirmishing and magic
• Why on Earth would an army with the technological level of the 15th century even think of using the thoroughly obsolete tactics and organization of an army a millennium and a half out of date? The Roman army of the early empire was a fine and great thing... for the 1st century before the common era. 1500 years later, not so much; among others, during this time, heavy cavalry became a thing, armor evolved, new tactics were developed. I would want to see a Roman legion of the early empire confront a charge of heavy lancers... – AlexP Mar 4 '20 at 0:00
• (And, BTW, those 35% women: why would anybody risk the lives of precious young women in a pre-modern army, especially an army modelled on the early-empire Roman pattern, with the main force consisting of heavy infantry? Does the emperor feel that the population of the empire is too large and must be reduced no matter what?) – AlexP Mar 4 '20 at 0:08
• To what extent does magic goes? Because the first thing that came to mind when I read "flexible and adaptable" was some kind of warforged army, as in magical constructs, built for war and with (in this case) the ability to partially reshape their body based on what they need (eg. more defense, more agility, specific weapons, and so on). If that's something your magic level would allow, then I think it's the answer. – Mr_Bober Mar 4 '20 at 1:08
• "Weapons and equipment are the same standards during Augustus though infantry don't carry pilum." Ahem, Pila were the Roman army's main ranged weapon, and their only armor-piercing one. The Roman legions depended very heavily on them; getting rid of the pila is a very bad idea. – The Daleks Mar 4 '20 at 1:46
• @dLord45 Keeping women out of combat wasn't about strength or skill, though that didn't help. Population is related to the number of women of childbearing age. Lose half your men and you can recover in a generation; lose half your women and it could take centuries to recover—if ever. So, unless women have far greater innate proficiency with magic than men to outweigh that, nobody will want them anywhere near combat. – StephenS Mar 4 '20 at 4:54

"More flexible and adaptable" actually has a name -- professional.

You get professional fighting forces through a combination of factors:

• Money: Professional forces aren't cheap. Used correctly, though, they tend to justify the expense.
• Professional Education: All leaders, from Generals to Sergeants, need academic education throughout their careers. They need to fully understand the tools (units, equipment) that they have available and how to employ them properly in common situations. They also need to understand likely enemy strategies and tactics.
• Professional Development: Skill training, combat training, leadership training, unit exercises, staff rotations, evaluations, etc. Leaders need to make their learning mistakes in a training environment so that they are proficient on real battlefields. Promotion should be based on merit and potential, obviously.
• Staffs: A proper staff coordinates and synchronizes the fight, conducts intelligence preparation, ensures proper logistics and good order, and prevents the commanders from getting swamped by irrelevant information. Rotating officers through staff positions broadens their experiences and makes them better leaders. They turn the overarching strategy into detailed operational plans with lines of effort and lines of advance.
• Specialization: Corps of skilled experts in intelligence and logistics and medicine enhance combat power. They enable smaller units to move faster, strike harder, and to be punch above their weight at being decisive. They focus combat power on useful objectives to further the overall strategy, and identify the weaknesses that the enemy is trying to conceal.
• Depots: Stores of replacement equipment and personnel make replacement operations (handled by those staffs) easy, keeping combat power high throughout a campaign.
• Money: Professional forces aren't cheap. — and that's where the world fails. Without slaveforce or mechanization the economy most likely won't be able to support this huge professional army. Few legions — maybe. Half a million of soldiers using manual labor of ~70 million semi-free peasants — never. – user28434 Mar 4 '20 at 15:50
• @user28434 I don't recall anybody saying that a professional army had to be huge. Expanding a professional core with large numbers of volunteers/conscripts during a contingency has long been a fully-expected task for many professional forces. Also, the concepts of military professionalism long pre-date industrialization. And, of course, the OP didn't set any treasury constraints. – user535733 Mar 4 '20 at 15:57
• The most soldiers he can possibly have as a standing army is 400,000 — ok, my bad, I thought it strictly 400k, and also I thought you're saying there should be 100% professional. concepts of military professionalism long pre-date industrialization — concepts — yes; wide scale implementation — no. OP didn't set any treasury constraints — the empire is 1. declining 2. just out of a civil war; we can assume treasury is not in good shape. Also, even they have huge stockpile of resources right now, the army may "eat it" quite quickly if the Empire doesn't upgrade its economy first. – user28434 Mar 4 '20 at 16:07

The emperor needs to introduce a staff college for training centurions of all ranks to give them a better understanding of strategy, tactics and a wider range of important military matters that could be learnt from a number of selected centurions who had encountered such situations.

The training would probably need to last a year or more. In this way new centurions would be better equipped to deal with a wider range of military situations that might be encountered such as sieges, river crossings, logistics, field manoeuvres, assaults on fortified positions, naval transport, communications, under mining enemy positions, construction of marching camps, use of auxiliary bowmen and artillery, etc etc.

The emperor also needs to listen to some of his most senior fighting soldiers (such as the Primi ordines) to find out what difficulties they have been experiencing and to address these issues head-on and correct them.

There would also be merit in establishing a wide range of auxiliary units from across the empire for specific specialist duties such bridging rivers, night attacks, defensive works, horse archers, heavy cavalry , light cavalry etc. These could then be used in conjunction with the legions by the trained senior centurions to good effect.

Leave it to his generals

Sun Tzu's Art of War is considered one of the defining manual on tactics and strategy, and was written a few thousand years ago. Seeing as that's the case, it's definitely good enough now.

To quote the venerable Sun Tzu:

There are three ways in which a ruler can bring misfortune upon his army:--

(1) By commanding the army to advance or to retreat, being ignorant of the fact that it cannot obey. This is called hobbling the army.

(2) By attempting to govern an army in the same way as he administers a kingdom, being ignorant of the conditions which obtain in an army. This causes restlessness in the soldier's minds.

(3) By employing the officers of his army without discrimination, through ignorance of the military principle of adaptation to circumstances. This shakes the confidence of the soldiers.

(The Art of War, Attack By Stratagem, 12-15; if you're curious. Though I'd recommend giving the entire book a quick read, it's not that long.)

The best thing the Emperor can do is to set a stable and meritocratic military, ensure that the generals are loyal, and then permit the generals themselves, who are going to be individuals of substantial military might and knowledge, the autonomy to give all the orders that are necessary.

Apart from the weapons/'tech-level', when you're working with the army of the late Republic, it's already as flexible as it gets.

The Marian reforms were implemented exactly to have a standing army, which implies an army that is quick to react, and consists of standard units capable of multiple tasks. Among the weaponry and cycling discipline of soldiers during battle, which helped to keep the soldiers alive and provided the Republic with victory over numerically superior opponents on a routine basis, the army also mastered the skill in altering battle field conditions.

Altering the battle field conditions was done via the corps of engineers, that were part of every legion. They would build forts, walls, ramps, blockades, everything to gain maximum advantage over the enemy, which was an important part of the army flexibility. For Romans this altering of battle-field conditions became such a natural way of preparing battle, that often no battle would be given, until a desired set of fortifications/blockades was constructed. This led to sometimes slightly comical situations, where for example, during the Caesar's civil war, Caesar and Pompey would race to build the longer wall for tens of kilometers in an attempt to enclose each other and cut off supply-lines and escape routes at the Battle of Dyrrhachium.

The republican army was designed with flexibility in mind. So while you certainly can implement some improvements, when analyzing their defeats (for example at the battle of Carrhae), just copy-pasting them you would already start with something very capable.

Wargames.

Both the tabletop variety, and actual soldiers fighting with blunt swords / nonlethal spells.

It allows commanders to try out tactics, it can force people to deal with unexpected circumstances (perhaps with a gamesmaster who comes up with unusual scenarios for them to face), and it can suggest who might be worth promoting.