KOREANS

History:
About the time when Rome was destroyed, the Koreans were in it's three kingdoms period. One being Koguryo, the other being Paekjae, and the last being Shilla. Shilla unified the peninsula with help of the Chinese Tang dynasty. But soon drove out the Chinese who planned on destroying Shilla and taking over the peninsula.
So came the unified Shilla period, which too, was soon divided into three kingdoms once again. Later-Paekjae was found in the old Paekjae's territory by Kyun-Hwon. In the north where Koguryo was, came Later-Koguryo, founded by Kung-Yae. Kung-Yae was a good king at first, but later became madand changed it's country's name many times, declared himself to be a living Buddha, killed many people including his sons,wife, and a lot of servants. It is said he killed 100 people a day. So Wang-Kon, a famous general, killed Kung-Yae and became king. He changed the name to Koryo. Koryo unified the peninsula yet again. That is the Koryo kingdom, which lasted for 500 years.
Towards the end of the Koryo dynasty, a famous general Yi-Song-Kye, turned his army at We-Hwa-do and took over. He declared himself king and opened the Choson dynasty. Choson was attacked by the Japanese at 1592. With the aid of Yi-Sun-Shin's turtle ships, generals, and China, Choson got rid of the Japanese. Although again attacked a few years later, they were able to drive the Japanese out again.
---Bonuses---

Team Bonus: +1 range for the mangonel/onager

Civ Bonuses:
Villagers +2 line of sight
Free tower upgrades. Bombard towers require chemistry first
Towers +1 range in castle age, +1 imperial age
Stone miners work 20% faster

+1 range for the mangonel/onager
A superb bonus, which can help other siege powerhouses, such as Mongols or Celts, as well as the Koreans. This allows the Koreans to have 12 range onagers(11 with the patch) which can outrange castles and towers. A very good bonus indeed.

Villagers +2 line of sight
Villagers having +2 LOS(+3 with the patch) is indeed a helpful bonus. It means you can spot enemy villagers building a forward base, and you can even scout with them. But this bonus becomes unhelpful in castle age and imperial age.

Free tower upgrades. Bombard towers require chemistry first
Free tower upgrades aren't too big of a deal, especially since in the patch tower upgrades don't require stone and a watch tower is nearly as good as a keep. But neverthless, you can have a keep filled with Korean arbalests which can be quite a good offense and defense. The bombard tower upgrade instantly means the Koreans can bombard tower push better.

Towers +1 range in castle age, +1 imperial age
The tower range bonus is a nice bonus if you use towers. That means that a FU keep has 13 range which takes away the possibility of a BC or Longbowman getting a tower provided that the tower has arabalests garrisoned in it.

Stone miners work 20% faster
Stone mining bonus compliments the 2 tower bonuses Koreans have. Also, with just a few villagers on stone in the dark ages, you can have instant access to a castle upon reaching castle age. A castle is very useful for the Koreans, since they can produce their powerful unique unit; the War Wagon.

---Strengths and Weaknesses---

-Strengths-

Towers
Towers should play an important role in the early ages. Since the Koreans are very vulnerable in the early ages, get a few towers with the stone mining bonus. About 2 or 3 towers can save your life against a flush. In castle age, you can make guard towers filled with crossbows near an enemy mining camp. This will slay many villagers, enough to more than make up for the few stone, gold, and wood you lost on the tower and crossbows.

Onagers
Onagers having a very long range, can outrange castles, pre-patched. They can slaughter longbows since they have the same range. With the Korean UT, Shinkichon(patched), your onagers have +30 attack bonus against buildings. This helps greatly, for onagers can now destroy buildings very fast. 5 onagers backed up with halberdiers and war wagons are long known to be unsoppable.

Archers
No remarkable bonus, but Koreans have every single archer technology except parthian tactics. Archers can also garrison into towers for added power, and massed archers can only be stopped by onagers, which the Koreans have the best of. HC can rid of any enemy infantry.

War Wagons
Possibly the best unique unit, it can destroy anything other than halberdiers and heavy cavalry. Massed war wagons with halberdier and onager back-ups, can destory anything.

Navy
No remarkable bonus, but the Turtle Ship(patched) allows the Koreans to comepete with other naval powerhouses. A single turtle ship can take out 3 galleons. Although slow and expensive, these mammoth ships can make the enemy galleons say bye-bye.

-Weaknesses-

Cavalry
Lacking both the last armor and attack upgrade for cavalry, this makes the Korean cavalry even worse than Vikings. Although they have hussars, a Korean hussar nearly dies to a Teuton scout cavalry. It survives with only 5 HP left, which places the hussar only good as raiders.

Infantry
They have both the champion and halberdier, but they lack blast furnace, an important upgrade. Neverthless, Koreans should still use infantry, just not as a bulk of their army. Halberdiers can protect the war wagons from falling from cavalry.

Early-Economy
The Koreans have a very bad early economy. But they have all economic upgrades which makes them a good economic civ. in the later ages. The Koreans are a very bad rushing civ, so use them as rush defense and late-age civilization.

--Through the Ages--

Dark Age
The Koreans' only strength is stone mining in the dark ages. Having 1 or 2 villagers on stone could mean a bit slower time, but instant access to a castle upon reachin the castle age. Do your usual build-up for they have no other bonus.

Feudal Age
This is the most critical age of the Koreans. They are not good here, but this is the age that they can be stopped. Survive here, you have a good chance of winning. A few spare towers could result in no instant access to a castle, but may save your life from a flush threat. Make wise decisions here, and try to get to the next age as soon as possible. Once you get over the Feudal Age, you're rocking and rolling.

Castle Age The castle age and imperial age is the Koreans' best time. As soon as you reach castle age, build a castle and start producing war wagons. Build some pikemen for support and a few mangonels. You can also build a few knights since there is nothing wrong with Korean castle age knights. But in imperial, do not upgrade to cavalier as they lack paladins, blast furnace, and plate barding armor. That makes them the worst in the game. Send them on a raid to the enemy town, while you keep booming at home base. War wagons should devastate the enemy. Once you see knights and/or pikemen, retreat and bring your own pikemen forward. Use your +1 range mangonels to destroy the enemy town center. Keep having the war wagons kill enemy villagers. Research archer upgrades at home. Once your army cleared away some of the enemy, bring a few villagers to build a few towers and a town center. Build an archery range and produce crossbows. When the enemy attacks your town center, garrison your crossbows in the tower to stop them. Build another tower near the enemy town center. Fill it with crossbows and the enemy can't ungarrison or farm. Try to go to imperial age quickly as well.
On water maps, produce turtle ships to kill enemy galleons. Once you have 20 turtle ships, know that you have controll of the sea. But do not waste too much on turtle ships, for once you get to imperial, it's not too late to control the seas.

Imperial Age
This is the Koreans' best age. Research elite war wagons, elite turtle ships, blacksmith upgrades, halberdier, and most importantly, the onager upgrade and Shinkichon. Make an army of halberdier, onagers, and elite war wagons to crush the enemy once and for all. Keep the same basic mind as in the castle age, except you have an upgraded version of it all.
Build more elite turtle ships on water maps to crush your enemy. The only civs that even have a chance to compete with the Koreans on water maps are Vikings, Saracens, and Byzantines. Research careening for +1 PA. Dry dock for making those turtles move faster, and shipwright for decreasing the cost of these expensive monsters.

--Combined Arms--

War Wagons
War wagons should play a big part in a Korean army. They seem expensive, but they're actually cheap for a unit that has lots of HP, PA, and attack. It's range has been decreased in the patch, but they're still a strong unit. A disadvantage is that they are produced from castles. But all unique units are produced from castles except huskarls and ship unique units, so that shouldn't be too big of a problem. A massed army of WW can crush the enemy.

Onagers
Korean onagers have 12 range in the pre-patched version and 11 in the patch. Patched onagers also have +30 damage vs. buildings which means onagers can flatten buildings really well, and from a distance. The onager can flatten longbows which have only 1 longer range. A few onagers with WW can be a good offense. They are also useful for smashing trebuchets. A Korean onager can take out a trebuchet from 11 tiles away from a trebuchet, instead of the usual 8.

Halberdiers
Okay, Korean halberdiers aren't the best in the game, lacking blast furnace. But they are useful for protecting the onager and WW from heavy cavalry. Since Koreans don't have good knights or camels, halberdiers are your best protection. A combo of halberdiers, onagers, and elite war wagons can't be stopped.

Arbalests
Arbalests are a good part in the Korean army. They can be fully upgraded, and the superb towers compliment them further. Arbalests, Halberdiers, and champions are a good combo. Throwing in some onagers might be nice as well. Korean arbalests can kill enemy infantry with the war wagons. Although I prefer war wagons, arbalests are easier to mass, which you should do.

Keep
A keep is researched automatically for the Koreans. Although most civilizations wouldn't use these, Korean keeps have their uses. Having 2 more range than a usual keep means they outrange longbows and bombard cannons. Since they fire only 1 arrow, garrisonning archers or villagers would be very good. They can also come in handy for killing enemy villagers.

Bombard Tower
Only chemistry is required to build these monsters. Send a few villagers immediately upon reaching imperial. Research chemistry on the way. Have some war wagons or arbalests protect the builders. A safe distance away from the enemy, build a bombard tower. Then in range of the bombard tower, build another one, and keep going into enemy territory with bombard towers. This is a bombard tower push. It can slaghter many villagers, and even a town center and houses. This will severely damage the enemy's economy.

Turtle Ships
Yes, the second Korean unique unit, the turtle ship. Before the patch, turtle ships were considered the worst unique unit, not to mention worst ship. With the patch, they are better than ever! A turtle ship can take out 3 galleons alone. 20 or so turtle ships, and the Koreans have control of the sea.

--Important Upgrades--

Elite War Wagon upgrade
This upgrade boosts the HP by 50, +1 PA, and +1 range. This is well worth the upgrade. Although the attack stays the same, the longer range allows 1 more hit for the enemy. More HP means it's more armored. 50 HP is a lot. It's 10 more HP than an arbalest, so it's having an arbalests' armor and 10 more HP. The extra PA is pretty good since it takes away the damage a War wagon takes from archers.

Onager
Onagers are much stronger than mangonels, with 10 more HP, 10 more attack,1 more PA, and 1 more range. The siege onager upgrade is also nice, but not worth the price unless you're playing on blackforest where you need to tunnel your way through flattening trees.

Chemistry
As for many civs, chemistry is a good technology. Not because of the +1 attack (which is nice to have), but the ability to get cannon galleons, bombard towers, hand cannoneers, and bombard cannons. The Koreans have good bombard towers, so researching chemistry is a must.

Shinkichon
The Korean unique technology, it adds +2 range in pre-patch, +1 range in the patch and +30 attack vs. buildings. That means a FU Korean Siege onager does 157 damage to buildings. This is a very good bonus, which allows the Korean onagers to destroy buildings with ease.

Blacksmith Upgrades
This is useful for all civilizations, but especially for Koreans since they have no attack bonus for their units. But the Koreans have a poor blacksmith, lacking 2 important technologies. Neverthless, blacksmith upgrades are still very useful in increasing your armys' power.