The Settlers III/Asian mission 6

The victory condition is complete control of the whole map.

Set up a basic settlement
Leave the two small islands to the East alone, you won't need them if following the strategy of this guide. Quickly build up a small settlement on the main island:
 * stonecutter, woodcutter, forester, and sawmill
 * a couple of fisherman huts
 * coal and iron mines

Having built the above, set the coal and iron mines to eat fish using the distribution of goods menu. Then continue building:
 * Iron smelter
 * Tool smith
 * A medium residence (you need a lot of pioneers for this level)
 * Ship builder and Landing Dock.

It's vital to get started on the uninhabited island to the West of the main island as soon as possible. Expand quickly South until there's enough room on the Western coast to build these two buildings.

Make some more tools. Remember to feed your miners.

Food and manna production
It will take some time to get production up to an acceptable level on this map. Make sure good trade routes are established between the main island and the Western island. Transfer a large group (20+) of pioneers to the Western island using a Transport ship. Make sure you send over 8 hammers, shovels and 4 of everything else early. When the pioneers have made a large enough land, build a stonemason, some woodcutters and a sawmill immediately to get local production up and going. Then make the island produce all your food needs and manna (rice wine). Send all the bread and meat produced here over to the main island for your coal and iron miners, then gradually reset the fish distribution to only gold mine again. As the wine distillery needs a steady supply of coal to operate, you may decide to place the distilleries and small temples on the Western island. Doing so will get you started earlier with promoting soldiers, which is important. So although there's little coal to find on the Western island, I recommend you keep manna production there. If necessary send coal from main island regularly to support the production.

Create a stronghold
As soon as possible (at the bend just South of the first swamp on the main island), place a stronghold consisting of a castle and a large guardhouse. This will serve as a defending point until your army is large enough to proceed. Build a healers quarters and a barracks near here and prepare for waves of enemies. It's a good idea to produce a lot of bowmen and put them up in the towers of your castle and guard houses as early as possible. The enemies will come in bursts, and you will lose a lot of soldiers, so make sure you have a steady production of weapons and settlers for your barracks. If you cannot find room to build residences on the main island, you can put your foresters on hold for a while (this will give you more room) and/or build large residences on the Western island (where there should be room if you have cleared away forest there).

Prepare for war
You won't be able to keep the enemies at bay forever, staying like this. In order to win, you need to create a second stronghold at the center of the main island (where the "arms" of the islands meet, just South of your first stronghold). There are two ways of taking this area. There's not much room for to build before this area. Only small guard houses unless you clear the stones and wait (which is a bad idea because this lets the enemy grow stronger). One way is to simply build your way down there using small guard towers. Again that may not be a good strategy either, as these small towers are easily overthrown by the enemy hordes. What I did was to gather a large enough army (40+ soldiers) and a bunch of pioneers (10+) then send the army to defend the area while pioneers take some land, enough to build at least two large guard houses (or one castle, but that takes longer to finish and is a bit risky). Make sure you have a full set of soldiers (3 spearmen + 3 bowmen) standing ready for each tower. You don't want this small stronghold to fall into enemy hands! With this temporary stronghold you should immediately start expanding with two castles in the center of the area. Like before, make sure they're filled immediately. If you don't have enough soldiers ready you can put the building on hold until you do have enough men. When this area is secured, the rest of the game shouldn't be too hard (the attack is described briefly in the summary).

Quick summary
Quickly get a decent production up and running on the Western island. Build up a stronghold consisting of a castle and a large guard tower to protect your main base. Hold back the enemy at this stronghold until your production has matured and you have a constant supply of soldiers. Send a task force of soldiers and pioneers and take the center area swiftly. Gradually build up this area until you have two castles and at least one large guard house. Keep a constant supply of soldiers to maintain your position here, and keep sending wounded to the healer. When you have amassed a great enough army (150+ soldiers), leave about 50 soldiers to defend the stronghold whilst attacking either one of your enemies, backed up by a priest or two. Keep the priests in almost front (not in front as they will get killed easily, and not too far behind as their spells will be out of range). Use the "Ch'in-Yuh's Shield" and "The Samurai Sword" spells on the front group of soldiers. Note that "The Samurai Sword" also works nicely on the bowmen. Heal up you wounded and fill up the defenses before proceeding with the attack until they are all defeated.