How to get Pax Romana Aeternum without losing cities.

Hello, everyone.
I apologize in advance for possible mistakes and typos, English is not my native language.
I know, that it is a bit late to post guide like this, but better late, than never.
I also hope that this guide will help you win this match and will save you from most troubles on your way to the Achievement.

As you have noticed, the situation is dire in this scenario. Your empire is unhappy, you have no money, you have no army, but you have enemy armies at your borders. Policies give you penalties, and it gets worse every time. But you should always keep in mind, that everything is fine. If someone managed to get this achievement, then you can do it also. But there are several thing you need to know, prior to starting.

The first thing is, that winning this scenario as Western Rome is nearly impossible on Diety. Period. Choose Byzantium. Otherwise, you will lose 4 cities in five turns with no way to possibly defend them, or reclaim them (seriously, 1 legion to defend four cities in France is not enough).

Second thing you need to know: you don't have to reclaim all allied cities. But combined Victory Points of your team must be greater, than those of every other player (separately, of course). So, if you have 4400 points, Western Rome has 1400 points and Sassanids have 5000 points (likely the most of your enemies), you will win, although the loss animation will still be played. Sad, but true.

To claim victory, however, you need to meet several requirements:
- good PC, because you will need to load often
- large amount of free time, because you might have to go back several turns, or even restart
- determination, because this scenario gets boring and frustrating after the first week
- luck, because reasons.

You will also need to save at the start of every turn, because to win without losing any of your cities means to keep all your units alive. I managed to keep it this way only until 38 turn, and then freaked out and started to ram clibanarii with composite bowmen. But cities didn't fall, at least.
My point is, that when you reach 35 turn you will already know, that winning this scenario is entirely possible, and you could finish it even without much planning. All you need to do, is to get your empire out of the mess at the start.

One of most dangerous parts of this scenario is culture.
Always keep in mind, that you will receive Policy penalties at 7, 12, 25 and 45 turns. If you manage to defend all your cities, you will only get four of them, and you are free to choose the least horrible. It should always be Rise of Serfdom, Barbarian Conscript, Usurper General and Neglected Infrastructure. Fighting with large rebel force will be difficult, but hopefully, it will appear somewhere, where it can be handled easily. But taking Neglected Infrastructure prior to this is not an option, because this way you will lose large amount of gold, which could've been spent on buying units.

First, you need to adjust food, production and gold income of cities, and choose, what they will build. You should completely stop city growth, or else unhappiness will reach it's deadly -10, and your units will receive 33% damage penalty. Also there is always a chance, that enemy will get to one of your luxury recourses and pillage them, taking away that precious happiness.
Byzantium can be virtually divided in sections, each of which will face it's own problems and have it's own duties:
Northern Greece: Sirmium, Naissus, Adrianapole, Thessalonica, Dyrrachium;
Southern Greece: Nicopolis, Athens, Mistra;
Cyprus: Attalia, Seleucia, Iconium, Ephesus;
North-East: Trebizond, Amaseia;
East: Theodosiopolis, Melitene, Edessa, Antioch, Damascus, Palmyra;
Middle: Constantinopole, Sinope, Amastris, Dorylaeum;
South: Cyrene, Ceasarea, Alexandria.

Southern Greece, Cyprus and South will have to deal with Vandal fleets, Northern Greece will be attacked by Goths, North-East is targeted by Huns and East - by Sassanids. As it has been told, you have no army, but you can actually create it from nothing in time.

Production:
(check "Show queue" checkbox in production panel to adjust queue )
South.
Cyrene - catapult (or circus), catapult, cataphract, marketplace, wealth
Alexandria - dromon, catapult, catapult, marketplace, wealth
Ceasarea - marketplace, wealth

Ceasarea doesn't have enough production to make units quick, so letting it build marketplace for future income is much better. Keep in mind, that if you will work sea tiles, the city will starve, once Vandal fleet blocks the sea.
You should build catapults in southern cities only if you intend on attacking vandal cities. Otherwise, you should build bowmen instead, or proceed directly to marketplaces and wealth.

East.
Theodosiopolis - bowman, marketplace, bowman, bowman, bowman, bowman
Damascus - cataphract, marketplace, wealth
Antioch - swordsman, marketplace, bowman, bowman, bowman, bowman
Edessa - spearman, bowman, marketplace, wealth
Melitene - spearman, bowman, marketplace, bowman, bowman, bowman
Palmyra - marketplace, wealth

North-East.
Trebizond - bowman, circus, bowman, bowman, bowman, bowman
Amaseia - cataphract, marketplace, wealth

Middle.
Constantinopole - swordsman, swordsman, bowman, bowman, barracks, dromon
Sinope - cataphract, harbor, marketplace, wealth
Amastris - cataphract, harbor, marketplace, wealth
Dorylaeum - cataphract, marketplace, wealth

Cyprus.
Ephesus - dromon, harbor, dromon, dromon, dromon, dromon
Attalia - scout, marketplace, wealth
Seleucia - scout, dromon, marketplace, wealth
Iconium - scout, marketplace, wealth

Southern Greece.
Nicopolis - dromon, dromon, dromon, dromon, dromon, dromon
Mistra - marketplace, dromon, dromon, dromon, dromon, dromon
Athens - marketplace, dromon, dromon, dromon, dromon, dromon

Northern Greece.
Sirmium - warrior, scout (or bowman), bowman, marketplace, bowman, bowman
Naissus - warrior, bowman, marketplace, bowman, bowman, bowman
Adrianapole - cataphract, bowman, circus, bowman (marketplace), bowman (wealth), bowman
Thessalonica - cataphract, cataphract (dromon), dromon, dromon, dromon, dromon
Dyrrachium - dromon, dromon, dromon, dromon, dromon, dromon

After you adjust production and work tiles, make new save (name it like Theodora_preparatio), so that you won't have to do all this hard and boring work in case you will need to restart.

Your main strategy for the whole game is to hole up in your territory and let none get inside. But in different regions it will look somewhat differently.

Your main strategy for the whole game is to hole up in your territory and let none get inside. But in different regions it will look somewhat differently.

Every time an enemy warrior gets 10XP, it will use insta-heal, and attack with full force again, so be careful about whom you attack.
Melee attack on city gives 7XP, on another enemy - 5XP, defense from distant city attack - 3XP, from another unit - 2XP. Keep that in mind, as it is useful not only in this scenario.
Also, if your defending unit gets promotion, you should consider using heal, if that unit is under 80% health, and increase in power for tile type, on which he stands, otherwise.
Next important thing is, that enemy melee warriors will usually stop advancing if there are no allies around, and they are damaged more than one turn walking from the city. They will heal for a long time, or even won't do it completely, so you have a good chance to stop some enemies in the middle of the field, if you injure them but don't overdo it.
Always prioritize units, that can deal large damage to cities, such as catapults, but, if you can surely obliterate melee unit, which is likely to capture city, then deal with him first.
Don't forget, that there is such thing as a Flanking Bonus. If you have two units near one enemy, each of them have 10% damage bonus, when attacking him. Use this in your advantage, when placing living walls, and also when making traps or advancing on enemy force. Trap example: If you place several units in line next to the city, but leaving gap between warriors and the city walls, enemies will try to squeeze there, to encircle the city. Then you will get (number you your units adjacent to that enemy - 1)*10% Flanking Bonus for every your unit (possible maximum is 50%).
When leveling up your ranged units keep adding bonuses to the same type of terrain: when you get three promotions, you could add bonus shot, or one tile to distance of attack. The same goes for ships, but they can get distance bonus at two same promotions instead of three.
Remember, that barbarians are getting points only when they capture city of any empire. Empires get points for controlling cities of any empire, cost also rises for having larger population in cities. Sassanids get 1.5 more points for city control. This all mean, that sassanids are your greatest threat, but also a possible source of bonus points, if you manage to capture any of their cities.
Remove unimportant roads. Harbor costs 3GPT, each tile of road - 1GPT. By removing roads and replacing them with harbors, you can win about 70-80GPT in this scenario.

All dromons at your disposal must rush to defend two cities: Mistra and Seleucia. Vandals will hit there will all their power, but if you protect both of them, enemy fleet won't bother you again. To successfully defend Mistra, you need three dromons: one from Cyrene, one from Mistra, and one from Constantinopole, the lower one. Remember to keep dromons away from the fighting, until all there are in place, one should always be hidden within the city. Also, don't let enemies step on crab tile, because, once trihemiolia is damage more, that 50%, it will pillage he resource. Also, try to keep that tile free all the time, to let any damaged dromon to swap place with one hidden in Mistra, to continue the offence.
Defending Seleucia is much harder and somewhat strange. You don't have anyone to defend it, and the closest dromon, which is near Alexandria, will be destroyed instantly, if it goes straight north. So order it to go west, and around deep sea part back to Seleucia. At the same time, Iconium, Seleucia and Attalia must build scouts, who will act like a gapholders. Sadly, those three are destined to die in several turns, but their noble sacrifice will save the city, because Vandal units tend to run aimlessly, if they can't encircle and attack city at first turn. This tactic will give you enough time to build dromons in Attalia and Seleucia and Ephesus, and lead them and Alexandrian one to finish off already damaged Vandal fleet.

This is actually the most difficult place to defend. You will have to send Melitene legion north, if you wish de protect Trebizond and Theodosiopolis, which means, that the only warrior on this front is Edessa legion, who will have to fortify on the hill next to Melitene. Interesting fact: enemies will target that guy most of time, because he is preventing them from encircling the city. To push the issue further, you must place spearman, build in Melitene, on the road to Edessa. It is also important to know, that right to the east of Melitene, river lies right on the border with Sassanid Empire. Keep that in mind, when calculating enemies' movement. Your strategy here is to hold up until cataphracts arrive from the middle region. After spearmen are finished, order bowmen.
Important thing: at 7-th turn you will receive your first policy, which takes away 2 production from every city with walls, including Melitene. You must adjust city production to build spearman at the same moment, as it was meant before, because otherwise he won't occupy needed tile (first northwestern hill, and then back to the city), and Sassanids will encircle Melitene and destroy it. At about tenth turn cataphracts from all over the middle will start to hatch, giving you that numbers you need. When they reach the city, use some hit and run tactics, targeting catapults or melee units, if they get to close to the city. Around this time you should also receive Great General, - put him inside the city. After the main storm subsides, you must place all your units on the road, forming the actual Theodosian Wall, and also blocking all small gaps between mountains in the north. If at some point of time enemy assault becomes completely unbearable, try to put Citadel in the eastern desert right next to Melitene. This place is ideal for Citadel, as enemies will lose all their movement, while crossing the river, and couldn't pillage it in one turn. But you should do your best to keep Great General intact, in case you will need to place Citadel at another place later.

Legion from Theodosiopolis must fortify on the hill east from Trebizond, while legion from Melitene would advance towards Theodosiopolis. Huns will flood the area instantly, impairing his movements, but you can use this to your advantage: one hunnic horseman will try to squeeze between two legions, and will instead stop right in the middle between two cities. There you can attack him, but don't use legions for this: both must stay as healthy as possible. The second legion, now Theodosiopolisian, must fortify in fortress to the east of the city, now to block advance of sassanid army. Keep in mind, that you must always target rams, because they deal huge damage to cities. Prioritize embarked ones, the only exception is when you can finish off another ram. For the first three turns the northern dromon from Constantinopole must go to Trebizond, to offer it more protection against embarked rams. Trebizond's legion should stay in one place, but at some point of time you will likely have to mobilize him, to finish off some units. At the end, you will turn hunnic army away at the last moment. After that, huns won't attack you for a long time.
Both cities must build bowmen, when cataphract from the middle will be finished, send couple of them here, to provide further protection against sassanids.

Here it is - your main army of four guys. Two of them, legion and bowman, must go west with one worker, and fortify near Adrianapole: bowman right to the west of the city, and legion - in the forest to the north-west from bowman. He and worker should both build there a fort. Important thing: you can order legion to build fort, then cancel it, and order worker to build it on the same tile, thus building it at double speed. When goths will get too close, fortify legion in almost finished fort and wait for trouble.
Another worker from Constantinopole should go to Amaseia and build road over the river, to let cataphracts advance without penalties.
Dromons must advance, as specified above: one goes to Trebizond, another - to Mistra.

It is pretty difficult part, but, perhaps, one of the easiest, because this place is attacked only once. Large force of Vandals will appear right next to Slelucia. To protect it, you must build scout in two turns in Seleucia, and in three turns in Attalia and Iconium. Seleucian scout should go one tile to the east and fortify there, scout from Iconium will go to north-west from first one, and from Attalia - to the nearest tile on the beach to Seleucia as possible. Vandal axemen will kill them, but in turn separate, leaving only half of their army at Seleucia. That half, in turn, will already get damaged, because neither land, nor sea units have any defensive bonuses at first turn. Target trihemiolias, and all will get better in time, because axemen are cowards and tend to run about instead of attacking cities. The greatest threat is that they can pillage copper mine. Anyway, dromons from Alexandria, Ephesus, Attalia and Seleucia would easily destroy Vandal fleet in matter of turns.

This is a bit tricky, because you must balance between offence and defense with your dromons. Keep in mind, that defeated ships will join enemy side, and on Diety chance of joining is about 100%. But, in fact, three dromons is enough to protect this city: one dromon from Mistra, one from Constantinopole and one from Cyrene. Place them in "L"-shaped formation, with upper dromon inside the city, and every turn bombard one enemy ship with all four attacks (including shot from Mistra), to obliterate it in one turn. This way you will quickly beat them down one by one, just remember to hide damaged dromon inside Mistra after first enemy attack. Ignore axemen until ships are destroyed, and turn on them at the end.
The only worker in Greece should run to Constantinopole, and start removing road to Attalia.

This part is as horrible, as the East, perhaps even worse at the start, because Goths will run freely all around without any rivers to stop them. Main strategy here is the same as there: build a wall. First part of it will be between Naissus and Sirmium: move legions out of the cities, one to the hills with diamonds, one - to the wheat fields, and fortify them. There is a good chance that they will never move again. both cities must build warriors: they can be upgraded later, but for now they just need to fill the gaps: one on the southern hill between legions, another - to the south-east of Naissus. He will be first to upgrade, because he has much less protection out there in the hills.
This formation will result in separation of gothic army to four parts:
- western, that circles around mountains and hills, getting to Dyrrachium,
- northern, that attacks Naissus,
- eastern, that attacks Adrianapole,
- middle, that attacks Thessalonica.
It is much more preferable, than having them all at Naissus. In time, Naissus and Sirmium will build bowmen, and deal with gothic threat with relative ease. But eastern part is much worse: after first heal, you will have to move legion out of the forest and hide him south from the city. About this time Adrianapole will finish cataphract, and Constantinopole - swordsman. Both of them must get to Adrianapole and fortify there, while sometimes attacking catapults, if they dare to cross the hills. In fact, despite the great numbers of goths attacking this city, it have the best position for defense, because enemies will lose their turns to move in hills, enemies can be attacked almost at any tile around the city by both city and bowman, that is stationed inside, and tiles, occupied by your units are usually out of reach for distant attacks. When pressure will be lowered, you must move your forces to the middle part of gothic army, to make them turn north, instead of attacking completely undefended Thessalonica. Be advised, that goths might not only pillage luxury resources, but also roads, loading to complete separation of Greece from Constantinopole, which will lead to loss of happiness and gold income. Keep that in mind when attacking enemies, and also that goths heal to 100% health for pillaging. But, if you play all your cards right, you can push enemy away.

Around 20th turn this strategies will completely turn away your enemies and obliterate their armies. But success relies mostly on luck and knowing if several hacks.
First: sometimes enemy units will completely ignore support units, such as Great Generals and workers. if you won't put them right in the way of enemy army, they might get out unnoticed.
Second: you can adjust the Great General's city of birth. Not directly and not completely, true, but you can make him appear in more preferable place than, for example, Alexandria. Choice of city, where GG is born, depends on several factors:
- total amount of experience gained by land units (7xp for melee attack on city, 5xp - melee on enemy, defense from distant city attack, or distant attack on city - 3xp, from/on another unit - 2xp),
- which unit deals the last blow,
- where last blow was dealt,
- amount of living enemies.
So, if you have several enemies, that might get killed by last city shot, consider waiting until GG is born in Antioch. Yes, you need at least two GGs on eastern front, because sassanids don't like to circle around, like goths, and will start to brutally ram your forces after some time. The sooner Great General gets inside Melitene, the better.
But, even knowing all this, it will still take a lot of time to get proper tactic of moving your units around to both save them and cities, so I'll post the log of their movement in first 17 turns here. Enemies are always trying to play their own way, but this log is sure to help anyway. But to understand it, first I'll explain some abbreviations and notation keys.
(Of course, if you wish to figure out how to play first 20 turns by youeself, feel free to ignore this description and table below.)
Each city can be shown as a field of 24 tiles. There are 5 rows, from north to south, each consist from 4 to 6 tiles (1st and 5fth has 4, 2nd and 4th - 5, and 3rd - 6). Center is tile 3.3, where center of coordinate is placed. Center of coordinates is specified by it's name: city name for cities, abbreviation for units.
For example, western hills right next to the Adrianapole are placed at Adrianapole3.2.
Units abbreviations:
l - legion,
b - bowman,
c - cataphract,
d - dromon,
w - worker,
s - spearman,
t - scout,
C - catapult,
W - warrior,
S - swordsman,
G - Great General.
Every unit has a number. They were named in sequence in which they first acted as I played, but it might be another way in your playthrough. Anyway, in table they will be named from top-left to bottom-right, to make it easier to perform in case everything happens the same way.

(u - up, r - right, d - down, l - left, a - attack, f - fortify, x - continue previous action, or do nothing)
Gothic front will be separated in east and north in this table.
If city attack is written with attacks on any front, or normal unit description order is disturbed, it means, that all actions must be done in this exact order for maximum effect.
If any newly created unit's movement is not specified, then: send all dromons and units from Cyrene and Alexandria to the west, put all bowmen on hills behind front lines to defend.

Decomposition by the names of fronts
It is, probably, important to do the following steps: b2, d2, Adrianapole, S3, c2, to spawn G2 in Antioch

(It was too large to fit in one Section Contents screen.)
reset production in cities to get more than -4 gpt
(In Sassanid part: Melitene, b6, l1, s1, c3, c1 exchange places with c3)

After this you can finish it by yourself. All you need to do, is build two more swordsmen and one cataphract in Constantinopole, and then continue making large numbers of dromons there, while also making new bowmen in all eastern cities and in Greece. Build marketplaces, circuses and stoneworks anywhere you can, to increase happiness and gold income, and play the same trick, as with Great Generals, when choosing where to spawn army of Usurper General.
Your main strategy for the rest of the game should be this:
Southern Greece, Thessalonica, Edessa, Dyrrachium: build dromons. Lots of them.
East and North of Greece: build bowmen.
Finish anti-goth wall, putting two more swordsmen in the fields to the west from Sirmium (tiles 3.2 and 4.1).
Send some troops to Salonae, to stop franks and goths from advancing further.
Send all your dromons to the west: four to Ravenna, eight to Genua and 4-6 to Iol Ceasarea. After that all further dromons must be separated equally between last two directions. Also take one cataphract to each fleet, so that it could deliver decisive blow on the city and reclaim it. And if you see approaching vandal fleet, don't try to destroy it completely, just focus on defending Iol Ceasarea, and reinforcements will finish the rest on their way here. Recapture Ravenna at the first possibility, to make franks fight for it instead of advancing, but be careful: city must have 0 hp to be captured by embarked unit. Also try not to lose that cataphract, and send him back to sea under protection of dromons at first signs of danger. Don't worry, if franks will recapture Ravenna after that, you will still have about 2000 victory points more than them at the end.
Attacking franks by land is almost useless, especially to reclaim Mailand. Franks have huge bonuses in hills and with adjacent allied units, so breaking through this is almost impossible, especially without fully leveled up ranged units (which will have +1 distance and +1 attack).
There are also many places on map, where it is most preferable to construct citadels,
and place bowmen, especially in the east, and north of Greece.

Green crosses - good places for melee units.
Red crosses - good places for archers.
Blue stars - good places for citadels.

Northern Greece.

And yet, I prefer to keep units on the road to increase their mobility and decrease the pressure on Naissus: this way it can be melee attacked only from 2 tiles.

East. Salonae defence force; it stood like this for about 30 turns. Also a good place for Citadel.

There is also one secret strategy: diversion. If you start attacking instead of defending, enemies will send their huge armies to destroy your attacking force instead of capturing cities. In my successful playthrough I didn't attack Sassanids, and they launched last 40-turn assault on Thessalonica, but I remember once that they attacked Melitene after I placed citadel near Amida:

The Spot.

The greatest thing about this hill is, that enemies can't see your units that are stationed there, and you can bombard city with catapults without them fighting back. Hint: you can place citadel in the tiles adjacent not only to your own, but also to ones owned by your allies; then they will be attached to your closest city (Sirmium in case of almost all northern part of Western Roman Empire).
Another good examples of diversion tactics are assault on Olbia and failed assault on Thagste. Latter one failed, and enemies destroyed 3 out of four catapults, but then their whole army got in the desert to find one cataphract. Olbia was bombarded by 7 dromons and captured, and then whole gothic army, that first started to attack Northern Greece at about 35th turn, turned east and reclaimed the city for some time.

Olbia.

And so, even though you won't be able to conquer the Earth, or live happily ever after in this scenario, you might hold all your cities for 70 turns needed to get the Achievement. Playing further is pointless, especially because at 130 turn or so you won't be able to continue: you will have to choose policy after all policies are taken, and your game will get stuck like this. But it doesn't matter, because you will win, you will get that difficult achievement, and most importantly, you will ruin game for Huns, leaving them with grand 0 points.

Sincerely,
realGuybrush.