First off, thanks to Molybdeus for starting this trend with his guide to Pacal. I hope people will start up a list of guides for Civ leaders and perhaps it will eventually be compiled into the War Academy. I have owned Civ 4 for...jeez, I forget how long now. I really love playing with leaders like Lizzie and Julius Ceasar but for the last month or so I have been playing only with leaders that I am less familiar with. It makes the game more interesting and challenging again. One leader I've been playing with for the last week or so is Justinian.
Spiritual
The spiritual trait allows you to switch civics the moment you gain access to them without falling behind. There are usually some civics that are almost always worth switching to, such as slavery, monarchy, caste system, organized religion, and vassalage. Add it up and you're looking at several turns of anarchy, not counting each time you need to switch religions. The spiritual trait will, in this way, keep you from falling behind a faster researching civ in the early game. The spiritual trait, however, really shines in the mid to late game. You can run bureaucracy and org religion and build some infrastructure, and then vassalage and theo to build an army, for example. While at peace you can run rep for the science boost and then switch to police state when the WW is eating you alive. Another use of the spiritual trait is for diplomacy: you can switch your state religion to make a quick tech trade or two or convince one civ to war against another, only to switch back 4 turns later.
Imperialistic
Some of you may remember when I started a thread a few weeks ago about how this trait sucks. Since then I have somewhat changed my mind. Aggressive is great for early warfare, but does nothing for naval units, air units, archery, mounted, armoured, seige...etc. You aren't always going to be relying on melee or gunpowder units and in many games you may indeed want cavalry to be the backbone of your army up until tanks. The exp boost provided by a GG applies to all units. The faster settler production helps you grab good city spots first (and this has synergy with Justinian, which I will discuss later). One thing about imperialist is that you can only benefit from the GG's if you are actually fighting. Therefore, I am going to propose something a little radical. When playing an imperialistic civ, it may make sense to, just for the hell of it, declare war on a neighbour with no intention of even invading his/her land. Why not pick a rival civ that is running ahead of you in tech and declare war on them, and then sit back and fight a defensive war? This will accomplish many things. First off, since you are defending, you have an advantage, and should be able to win most battles, thus whittling away his military while maintaining your own. You will therefore keep his power rating in check and, more importantly, slow down his research. The real reason you are doing this, however, is to pop those GG's. You are basically using your rival to give you GG's and then you can settle them in your cities, giving you an exp boost. Since the fighting is taking place in your borders you will suffer no war weariness and your rival will. Keep in mind, if you are strong enough to actually beat him in a war then just do that, this defensive war tactic is merely a strategy I have thought of to exploit the imperialistic trait even when I am too weak to conquer a neighbouring civ. And now, on to Justinian specifically.
Justian of the Byzantines
Spiritual and Imperialistic
Starts with Mysticism and The Wheel
UU: Cataphract: a 12 strength knight
UB: Hippodrome: a theatre that grants 2 happy faces per 10% slider and 1 extra happy face with access to horses.
So Justinian has an easy time raising his happiness cap and can command an extremely powerful knight. What are some strategic options?
Early Game
Justinian is a warmonger and shouldn't chase after wonders. That said, the two best wonders for him are right at the beginning of the game: the Oracle and the Great Wall. This is rather annoying as there are so many things for you to be doing at that point in the game. If you go for Polytheism you have no worker techs. I would say look at your starting position and decide which path to take. You can go for Hinduism and the Oracle if you have marble and/or a commerce tile to work right away (to research polytheism first). If you have a good hammer start and/or stone, the Great Wall would be a better choice. Personally, I think the Great Wall is probably more important for Justinian than Hinduism. You can found other religions throughout the game quite easily and can capture holy cities with your military. The Great Wall will help Justinian in two ways: exploiting his imperialistic trait and giving him a Gspy or two (and he relies on espionage heavily in the late game). Therefore, I recommend going for the GW. Also, by grabbing bronze working you can have something for your worker to do. If you start with marble or stone in your BFC you could build a worker first for road building. Another option would be to get agriculture and animal husbandry. First, it allows you to develop your land and, second, Justinian REALLY REALLY REALLY needs horses!!! He needs them for both his UU and UB. Find those horses and hook them up at all costs. If you don't have horses your first war should have the primary aim of capturing a city with horses...I'm not even kidding. And so that is the early game.
Now let's look at the Economy:
Since he starts with mysticism, trying to found an early religion is very possible. He is neither philosophical nor financial nor industrial and thus will not have an economy boosted by financial cottages or pyramid specialists or even quick great people. Justinian, for the first half of the game, will get the gold necessary to run his empire from religious shrines. It is quite doable to grab 2 or 3 religions fairly early on, by going for polytheism right away, and then monotheism shortly thereafter, followed by writing, and a beeline to code of laws. Of course, you will need to research other techs during this time as well, which is why I said you can found 2 OR 3. 3 if you're lucky and playing on Prince, probably only 2 if playing on monarch or higher. You should think about building the oracle. It is not out of the way for you, Justinian, since you are researching religious techs anyway. It is a cheap wonder and possible to build even lacking marble or the industrial trait, so long as you have a city with decent production and/or forests. The oracle will help you get a great prophet to build those shrines. I have built stonehenge with him but I find it only marginally useful. Stonehenge is a very strong wonder for charismatic civs or civs that need a great prophet but can't afford to detour to the oracle. Justinian doesn't really need stonehenge, however, and would probably be better off using that early production to pump out some more settlers (taking advantage of the imperialistic trait). Take advantage of the fast settlers and grab a few early cities, one or two being high hammer cities and one or two being high food cities. Religion will pop your borders for you and help with the happy cap, and an early shrine will help you pay for those cities.
So Justinian can get a large empire going and pay for it by founding two or three religions and building one or two shrines, spamming his religions to his cities and to AI cities. Code of laws not only grants a religion but allows him to run specialists and that is why grabbing high food cities early on is important. You'll need them for scientists and merchants. Since he is a religion whore you should be able to get at least one or two AIs to adopt one of your founded religions, providing you with further coinage. In fact, Justinian seems to never have problems producing gold, it's beaker production that is a challenge for him. One way you can try to compensate for this is if you have several relgions you can build many monastaries. Remember that each monastary grants a 10% bonus to science output. That adds up.
Once code of laws has been researched, it's already time to start thinking about beelining for guilds. This, of course, will let you build the cataphracts and grocers. Grocers are important for Justinian, who has little worries about happiness but needs health, and a grocer in his shrine cities will really pay off. Ironically, since he researches through the monarchy path and has all those religions, the hippodrome isn't even that much of a concern right away. It is infinitely useful, however, for dealing with WW and will be very important when switching out of hereditary rule later in the game.
What about his military?
At some point in the early game, while you are setting up all those religions, you will need to be building up a military. This is why I recommended grabbing a couple of high hammer cities right from the get-go. Because Justinian is focusing on founding religions early on and spamming missionaries, you cannot do this and at the same time rush your enemies with axes. The Byzantines do not have an ancient or classic age UU. Justinian can pull off an axe rush as well as anyone else, and by all means you should go ahead and do this given the chance. If you have horses it might be worthwhile to actually try and fight an early war with horse archers. They can later be upgraded to cataphracts and you will need horseback riding eventually anyway.
Remember my schpeal about a defensive war? Even if you aren't strong enough to fully conquer one of your rivals, you may want to to declare war anyway, just to give your units some target practise. This is especially true of your mounted units. Horse archers aren't the best units for taking cities as they cannot receive the city raider promotion, but they shine in the field. The only units that can take them on in the field are spearmen and swordmen, and swordmen are probably still at a disadvantage. If you find yourself with horses but no copper or iron, at least fight a defensive war for the purpose of promoting your mounted army. You can do many other things with horse archers too, such as crippling your neighbour by stealing his workers and pillaging his land. What I like to do with Justinian is grab HBR fairly early and spam HA units with a few axemen to counter spears. If I can't take enemy cities easily I will pillage/worker steal and then sit back and wait for him to cross into my borders so i can pop GGs. This will really slow down my rival so that later on when i get catapults I can take his cities with greater ease.
Finally, once you are confident that your economy can stand on its own two feet (you have code of laws for merchants and scientists and have currency), you should be thinking about going for guilds. As stated before, the grocer is super important for Justinian as happiness is abundant for him but health is not, and the grocer will pay hansomely in shrine cities.
Whether you go for guilds or engineering first is up to you, and they have similar tech paths, but I usually go for guilds first. Cataphracts + catapults is stronger than trebuchets + horse archers. So I rush to guilds. Once you have cataphracts, the game becomes very interesting. Cataphracts make short work of longbows and macemen, and can even hold their own against pikes, especially if you give them the shock promotion. Enemy cities will fall quickly to your cataphracts. Don't forget to bring some axes to deal with pikes (as you probably won't have macemen if you have followed my beeline example) and some longbows to defend enemy cities once they are yours. Also, don't forget that the cataphract is a mounted unit. Take advantage of the two movement points. Run deep into enemy territory and pillage strategic resources such as copper and iron. Also, remember the cataphract gets a flanking attack against catapults and trebuchets, should the enemy try to use any. You should be able to destroy most enemy seige units before they can even be used against you. This will help protect your stacks and help you in those defensive wars.
Later Game
After you have conquered a massive empire, you will probably want representation for the science boost and then biology for more specialists. The hippodrome takes care of the happiness side of caps and thus health resources are extremely important for you. Trade for them or take them by force. You will probably be running representation, bureaucracy, caste system, and state property.
You could, of course, run a cottage economy with Justinian, but I don't find that particularly useful for him. With him I like to have just 2 types of cities: food and hammers....and actually I often wind up having cities that are high in both. You'll want to make a super money city - with a shrine or two, a wallstreet, and tons of merchants. You'll also have several scientist cities. In the early game you'll run a lot of priests to get those prophets and shrines, but they aren't as important later on. Then you'll have hammer towns with workshops and watermills. Caste system and SP make those workshops amazing, and watermills will give you food and hammers under SP. So I usually run a specialist and hammer economy with Justinian. I will admit that beakers are difficult to come by. The reason is that Justinian will not get the pyramids (unless you have stone right away) and he his not philosophical...plus your first 2 or 3 GP are going to be prophets anyway. One solution to this is to run a lot of spy specialists later on in the game and if you are the first to state property you can use your Gspy to build a scotland yard and thus a super spy city. You can then use the espionage points to steal techs from your more advanced foes. One thing that sucks about beelining to state property is that scientific method, on the way, obsoletes your monastaries. Given that, I would recommend even changing some of your scientists to spies. Monastaries are really the only way Justinian can even hope to keep up in tech. Without them your scientists are less useful. Also, everyone by now knows that you get more bang for your buck using espionage for techs anyway. A spy gives you, what, 4 esp points? The two spy buildings raise your esp output by 100% making each spy give you 8 points, and a scientist only gives you 3, plus a 50% boost from the library and uni makes it 4.5. (don't count representation as that will boost spies as well as scientists). The espionage points required to steal a tech are also less than the beakers required to research it (so I've been told) and thus you can get more out of spy specialists than scientists later in the game. You can then achieve tech parity. The only disadvantage to this is that you will have to rely on the AIs to research techs, not being very good at researching them yourself.
Summary
Justinian is a warmonger, no doubt about it. Focus on your military, particularly your cavalry. Wonders are a low priority, besides, he can take them by force. Two wonders that make sense for Justinian are the Oracle and particularly the Great Wall. The GW will let him REX without worrying about barbs, pop more GGs, and help him in his spy game. He can found religions and has a super-happiness producing UB and thus health is the greater concern for him - find health resources or take them by force. His economy is weak - you will need shrines for gold and monastaries for research or you will stagnate economically. I find beelining for code of laws (caste system) and then guilds is strong with him. Trade for backfills. Specialists and workshops/watermills work well with him - and so does State Property. Espionage is the only thing that will give you the ability to have tech parity in the late game - to play Justinian in the late game you must know how to use the espionage system. Good luck.
Spiritual
The spiritual trait allows you to switch civics the moment you gain access to them without falling behind. There are usually some civics that are almost always worth switching to, such as slavery, monarchy, caste system, organized religion, and vassalage. Add it up and you're looking at several turns of anarchy, not counting each time you need to switch religions. The spiritual trait will, in this way, keep you from falling behind a faster researching civ in the early game. The spiritual trait, however, really shines in the mid to late game. You can run bureaucracy and org religion and build some infrastructure, and then vassalage and theo to build an army, for example. While at peace you can run rep for the science boost and then switch to police state when the WW is eating you alive. Another use of the spiritual trait is for diplomacy: you can switch your state religion to make a quick tech trade or two or convince one civ to war against another, only to switch back 4 turns later.
Imperialistic
Some of you may remember when I started a thread a few weeks ago about how this trait sucks. Since then I have somewhat changed my mind. Aggressive is great for early warfare, but does nothing for naval units, air units, archery, mounted, armoured, seige...etc. You aren't always going to be relying on melee or gunpowder units and in many games you may indeed want cavalry to be the backbone of your army up until tanks. The exp boost provided by a GG applies to all units. The faster settler production helps you grab good city spots first (and this has synergy with Justinian, which I will discuss later). One thing about imperialist is that you can only benefit from the GG's if you are actually fighting. Therefore, I am going to propose something a little radical. When playing an imperialistic civ, it may make sense to, just for the hell of it, declare war on a neighbour with no intention of even invading his/her land. Why not pick a rival civ that is running ahead of you in tech and declare war on them, and then sit back and fight a defensive war? This will accomplish many things. First off, since you are defending, you have an advantage, and should be able to win most battles, thus whittling away his military while maintaining your own. You will therefore keep his power rating in check and, more importantly, slow down his research. The real reason you are doing this, however, is to pop those GG's. You are basically using your rival to give you GG's and then you can settle them in your cities, giving you an exp boost. Since the fighting is taking place in your borders you will suffer no war weariness and your rival will. Keep in mind, if you are strong enough to actually beat him in a war then just do that, this defensive war tactic is merely a strategy I have thought of to exploit the imperialistic trait even when I am too weak to conquer a neighbouring civ. And now, on to Justinian specifically.
Justian of the Byzantines
Spiritual and Imperialistic
Starts with Mysticism and The Wheel
UU: Cataphract: a 12 strength knight
UB: Hippodrome: a theatre that grants 2 happy faces per 10% slider and 1 extra happy face with access to horses.
So Justinian has an easy time raising his happiness cap and can command an extremely powerful knight. What are some strategic options?
Early Game
Justinian is a warmonger and shouldn't chase after wonders. That said, the two best wonders for him are right at the beginning of the game: the Oracle and the Great Wall. This is rather annoying as there are so many things for you to be doing at that point in the game. If you go for Polytheism you have no worker techs. I would say look at your starting position and decide which path to take. You can go for Hinduism and the Oracle if you have marble and/or a commerce tile to work right away (to research polytheism first). If you have a good hammer start and/or stone, the Great Wall would be a better choice. Personally, I think the Great Wall is probably more important for Justinian than Hinduism. You can found other religions throughout the game quite easily and can capture holy cities with your military. The Great Wall will help Justinian in two ways: exploiting his imperialistic trait and giving him a Gspy or two (and he relies on espionage heavily in the late game). Therefore, I recommend going for the GW. Also, by grabbing bronze working you can have something for your worker to do. If you start with marble or stone in your BFC you could build a worker first for road building. Another option would be to get agriculture and animal husbandry. First, it allows you to develop your land and, second, Justinian REALLY REALLY REALLY needs horses!!! He needs them for both his UU and UB. Find those horses and hook them up at all costs. If you don't have horses your first war should have the primary aim of capturing a city with horses...I'm not even kidding. And so that is the early game.
Now let's look at the Economy:
Since he starts with mysticism, trying to found an early religion is very possible. He is neither philosophical nor financial nor industrial and thus will not have an economy boosted by financial cottages or pyramid specialists or even quick great people. Justinian, for the first half of the game, will get the gold necessary to run his empire from religious shrines. It is quite doable to grab 2 or 3 religions fairly early on, by going for polytheism right away, and then monotheism shortly thereafter, followed by writing, and a beeline to code of laws. Of course, you will need to research other techs during this time as well, which is why I said you can found 2 OR 3. 3 if you're lucky and playing on Prince, probably only 2 if playing on monarch or higher. You should think about building the oracle. It is not out of the way for you, Justinian, since you are researching religious techs anyway. It is a cheap wonder and possible to build even lacking marble or the industrial trait, so long as you have a city with decent production and/or forests. The oracle will help you get a great prophet to build those shrines. I have built stonehenge with him but I find it only marginally useful. Stonehenge is a very strong wonder for charismatic civs or civs that need a great prophet but can't afford to detour to the oracle. Justinian doesn't really need stonehenge, however, and would probably be better off using that early production to pump out some more settlers (taking advantage of the imperialistic trait). Take advantage of the fast settlers and grab a few early cities, one or two being high hammer cities and one or two being high food cities. Religion will pop your borders for you and help with the happy cap, and an early shrine will help you pay for those cities.
So Justinian can get a large empire going and pay for it by founding two or three religions and building one or two shrines, spamming his religions to his cities and to AI cities. Code of laws not only grants a religion but allows him to run specialists and that is why grabbing high food cities early on is important. You'll need them for scientists and merchants. Since he is a religion whore you should be able to get at least one or two AIs to adopt one of your founded religions, providing you with further coinage. In fact, Justinian seems to never have problems producing gold, it's beaker production that is a challenge for him. One way you can try to compensate for this is if you have several relgions you can build many monastaries. Remember that each monastary grants a 10% bonus to science output. That adds up.
Once code of laws has been researched, it's already time to start thinking about beelining for guilds. This, of course, will let you build the cataphracts and grocers. Grocers are important for Justinian, who has little worries about happiness but needs health, and a grocer in his shrine cities will really pay off. Ironically, since he researches through the monarchy path and has all those religions, the hippodrome isn't even that much of a concern right away. It is infinitely useful, however, for dealing with WW and will be very important when switching out of hereditary rule later in the game.
What about his military?
At some point in the early game, while you are setting up all those religions, you will need to be building up a military. This is why I recommended grabbing a couple of high hammer cities right from the get-go. Because Justinian is focusing on founding religions early on and spamming missionaries, you cannot do this and at the same time rush your enemies with axes. The Byzantines do not have an ancient or classic age UU. Justinian can pull off an axe rush as well as anyone else, and by all means you should go ahead and do this given the chance. If you have horses it might be worthwhile to actually try and fight an early war with horse archers. They can later be upgraded to cataphracts and you will need horseback riding eventually anyway.
Remember my schpeal about a defensive war? Even if you aren't strong enough to fully conquer one of your rivals, you may want to to declare war anyway, just to give your units some target practise. This is especially true of your mounted units. Horse archers aren't the best units for taking cities as they cannot receive the city raider promotion, but they shine in the field. The only units that can take them on in the field are spearmen and swordmen, and swordmen are probably still at a disadvantage. If you find yourself with horses but no copper or iron, at least fight a defensive war for the purpose of promoting your mounted army. You can do many other things with horse archers too, such as crippling your neighbour by stealing his workers and pillaging his land. What I like to do with Justinian is grab HBR fairly early and spam HA units with a few axemen to counter spears. If I can't take enemy cities easily I will pillage/worker steal and then sit back and wait for him to cross into my borders so i can pop GGs. This will really slow down my rival so that later on when i get catapults I can take his cities with greater ease.
Finally, once you are confident that your economy can stand on its own two feet (you have code of laws for merchants and scientists and have currency), you should be thinking about going for guilds. As stated before, the grocer is super important for Justinian as happiness is abundant for him but health is not, and the grocer will pay hansomely in shrine cities.
Whether you go for guilds or engineering first is up to you, and they have similar tech paths, but I usually go for guilds first. Cataphracts + catapults is stronger than trebuchets + horse archers. So I rush to guilds. Once you have cataphracts, the game becomes very interesting. Cataphracts make short work of longbows and macemen, and can even hold their own against pikes, especially if you give them the shock promotion. Enemy cities will fall quickly to your cataphracts. Don't forget to bring some axes to deal with pikes (as you probably won't have macemen if you have followed my beeline example) and some longbows to defend enemy cities once they are yours. Also, don't forget that the cataphract is a mounted unit. Take advantage of the two movement points. Run deep into enemy territory and pillage strategic resources such as copper and iron. Also, remember the cataphract gets a flanking attack against catapults and trebuchets, should the enemy try to use any. You should be able to destroy most enemy seige units before they can even be used against you. This will help protect your stacks and help you in those defensive wars.
Later Game
After you have conquered a massive empire, you will probably want representation for the science boost and then biology for more specialists. The hippodrome takes care of the happiness side of caps and thus health resources are extremely important for you. Trade for them or take them by force. You will probably be running representation, bureaucracy, caste system, and state property.
You could, of course, run a cottage economy with Justinian, but I don't find that particularly useful for him. With him I like to have just 2 types of cities: food and hammers....and actually I often wind up having cities that are high in both. You'll want to make a super money city - with a shrine or two, a wallstreet, and tons of merchants. You'll also have several scientist cities. In the early game you'll run a lot of priests to get those prophets and shrines, but they aren't as important later on. Then you'll have hammer towns with workshops and watermills. Caste system and SP make those workshops amazing, and watermills will give you food and hammers under SP. So I usually run a specialist and hammer economy with Justinian. I will admit that beakers are difficult to come by. The reason is that Justinian will not get the pyramids (unless you have stone right away) and he his not philosophical...plus your first 2 or 3 GP are going to be prophets anyway. One solution to this is to run a lot of spy specialists later on in the game and if you are the first to state property you can use your Gspy to build a scotland yard and thus a super spy city. You can then use the espionage points to steal techs from your more advanced foes. One thing that sucks about beelining to state property is that scientific method, on the way, obsoletes your monastaries. Given that, I would recommend even changing some of your scientists to spies. Monastaries are really the only way Justinian can even hope to keep up in tech. Without them your scientists are less useful. Also, everyone by now knows that you get more bang for your buck using espionage for techs anyway. A spy gives you, what, 4 esp points? The two spy buildings raise your esp output by 100% making each spy give you 8 points, and a scientist only gives you 3, plus a 50% boost from the library and uni makes it 4.5. (don't count representation as that will boost spies as well as scientists). The espionage points required to steal a tech are also less than the beakers required to research it (so I've been told) and thus you can get more out of spy specialists than scientists later in the game. You can then achieve tech parity. The only disadvantage to this is that you will have to rely on the AIs to research techs, not being very good at researching them yourself.
Summary
Justinian is a warmonger, no doubt about it. Focus on your military, particularly your cavalry. Wonders are a low priority, besides, he can take them by force. Two wonders that make sense for Justinian are the Oracle and particularly the Great Wall. The GW will let him REX without worrying about barbs, pop more GGs, and help him in his spy game. He can found religions and has a super-happiness producing UB and thus health is the greater concern for him - find health resources or take them by force. His economy is weak - you will need shrines for gold and monastaries for research or you will stagnate economically. I find beelining for code of laws (caste system) and then guilds is strong with him. Trade for backfills. Specialists and workshops/watermills work well with him - and so does State Property. Espionage is the only thing that will give you the ability to have tech parity in the late game - to play Justinian in the late game you must know how to use the espionage system. Good luck.
(a little graphic to spice things up) 
that you can use to ramp up the research rate for a while. Indeed, taking it off your build list will allow another city to repeat this process if there is the appropriate opportunity, but it is likely that there will be more important builds underway.
.
for a while.
.
... I've left it hanging on a knife edge. 
