Age of Empires II: The Age of Kings/The Horde Rides West

This scenario poses an unusual problem. You start with two bases, and there is no way to shift your forces between them until quite near the end of the scenario. Some people might suggest abandoning one position entirely, but this is unreasonable for several reasons. First, the northern base must be kept because Subotai is there, but your only source of stone and your best early source of food is in the south. Second, if you abandon the south, you are handing over all those resources plus a lot of gold to the Persians. Third, it really isn't necessary. You will be stretched fairly thin for a time, and there is one other difficulty that will be mentioned later, but that only makes the scenario harder; it doesn't make it hard.

Your first objective is to get some scouts out there. (Isn't that always true?) In the north, you have a bunch of cavalry archers. They are not ideal scouts by any means, but at least they are fast, so we are going to stick with them for now. In the south, you have very limited scouting capacity, so build a Stable immediately, which uses up almost all your starting wood stockpile. Put all other villagers on wood collection, and produce four more. Produce one scout cavalry in the south; now your food is also used up or allocated (but check the spoilers). You have enough gold for two monks, so don't bother collecting gold yet. You can start collecting stone when both food and wood are rolling in.

In the south, you have been instructed to assassinate the Shah, and it is suggested that you do this immediately. Since you have no way of knowing what will happen if you delay or refuse, just do it right away. You also have no idea whether your assassins will be ambushed, so send your two cavalry archers along as escorts. Kill two birds with one stone by scouting with them at the same time. The cavalry archers need to stay outside the Persian territory.

In the south, you start finding sheep immediately, and you should eventually get 10. The Persians are already scouting this area, but any sheep that they find before you must wander in through their front gate, and you should be able to intercept them. Your Outposts will help with this. The sheep will provide about 850 food, and after that you have other animals to hunt. Don't bother with farming until much later.

In the north, you find a small Merkid camp and a bunch of wolves. Don't fight the Merkids until you have fully scouted their camp. Avoid fighting the wolves for now, because you have better things to do. However, these wolves are hungry and will actually chase your cavalry. Not that they will gain by it. When employed properly, one Cavalry Archer can easily kill one wolf without taking any damage.

The Merkids and points west
The Merkids have no autonomous economy and only two cavalry archers. In principle, they could produce a lot of archers, and they may even have other things going on elsewhere. You should attack them as soon as you have fully scouted their camp. As a general rule, an AI will surrender when it has no units left. You don't know exactly how this will play out here (it actually makes no difference whatsoever), but you should aim to kill both Merkid cavalry archers fast enough that they cannot be replaced in time to save themselves. You can expect to have monks quite soon, so avoiding damage is not critical, but it's just good tactics to avoid damage wherever possible.

When the Merkids surrender, they hand over some Archery Ranges and Houses, as well as a few other buildings and access to significant gold deposits. By the time this happens, the assassins should have done their dirty work, and you will have finished exploring the SE area of the map. You now have access to 20 gold mines, which is plenty, and 5 stone mines, which is not. You may be able to claim some stone from the Persians, but don't count on it.

Immediately after defeating the Merkids, scout to the west. That's where you will find the Russians. Pay close attention to your scouts. They don't have a great sight range, and the Russian castle can do a number on one of your Cavalry Archers. The Russians are active, and will be attacking you soon. Their attacks will be fairly powerful, but as long as you have some stonework and a mobile force, you should be OK.

One significant problem in this scenario is that, unless you do Market manipulations, you can only afford one castle for defense. It has to be in the south, because that's where you will be facing war elephants. This means that you will not have trebuchets in the north, and therefore you will need to work with lower-tech siege weapons. If you intend to take on the Russian castle directly, you will need five battering rams, and a couple of small catapults may be useful as well. However, you may be able to crush the Russians just by raiding their economy. In any case, you should be raiding the Russians. Continue to explore; you will be able to get all the way to the north gate of Samarkand.

The Persians
Most of the action in this scenario is against the Persians, and the primary battlefield is in the south. Fighting Persians means fighting war elephants. There are several ways of dealing with War Elephants, but we are only going to use the main one, which is possessing them. Basically, every second War Elephant produced by the enemy is a War Elephant produced for you, and the other ones are just targets. Of course, you do need a lot of monks, and you need to make other preparations.

You will need a castle, and you will need a Wall Maze Complex. You will also need other supporting units. Because you have so little stone, and because the south is so open, your WMC will focus on the maze aspect. That is, you will be using wooden walls. Your WMC doesn't need to be very sophisticated. Just build one long channel ending in front of your castle. Your monks and archers stand on one side of the wall, and the attacking force crawls by them. If necessary, the monks can hide in the castle. Nothing will penetrate this defense.

Other than that, there really isn't much to say. Grab what you can, raid when you can, defend when you must. Start building defenses as soon as you have 20 or so villagers and a viable economic base. Try to get to the population limit before you have to possess a lot of enemy units. Don't bother keeping any of the War Elephants unless they are fully upgraded. Once you have pushed the Persians back to their main gate, there are a lot of choke points, so you will be building stone walls in the SW part of the map. Eventually, one way or another, you will build up a stone stockpile, and you will need to build at least one castle in the Persian area.

There is one wrinkle in the north. There is a river leading into the north part of the Persian city. It would be very useful for you to have one Transport Ship and one Cannon Galleon operating on that river.