Age of Empires II: The Conquerors/Brother against Brother

Map
Available on the Steam website.

Walkthrough
Move to the King, fight the opponents and get the horse by walking up behind the king close towards the stable. After the dialogue finishes, you will get an army and a few villagers.

The mission will end if you have entered the enemy town and defeated its defenses, then return with the blue king back to the area where you did the fighting in the beginning.

Tips

 * You start with a lot of units and not much wood, so you will be hindered building houses to cope with the population limit. So with your El Cid unit, ride towards the town in the north, they will cheer at you and give you a few houses for free. Then ride the road south toward the center of the map, behind the bridge a village will join your cause, so you get a few more houses and a mill with fields.
 * You can take your time with the build-up because the enemy will neither attack you nor rebuild units (on standard difficulty).
 * Although you won't need many ressources, you might want (maybe just as a matter of principle) to hurry grabbing stones before the others take too much of it. Your ally (yellow) has a quarry in the northeast, between your starting area and his town. And your enemy's quarry is in front of his town walls. A good idea is to kill his villagers there, use only the El Cid unit. That will lure out most of his army, but you can pull them toward one of your ally's castles in the southwest or southeast and let them be killed while you recover inside.
 * You will encounter two small groups of conquistadors who join you, but you might want to stay away from them until you have built enough houses so that the extra units don't block the creation of villagers.
 * In the west is a large forest, hidden behind it is a monastery, six monks and four relics that will join you when you managed to hack your way through the woods and explore the area with the El Cid unit.
 * It is a good idea to waste the infantry units you start with by razing the towers in the west, so they don't hamper your villager production any longer.
 * There is way enough gold on the map, but if you want to build a market, the northern corner seems to be ideal, if put on the edge the ally's market will yield 25 gold and the carts can drive a straight line.
 * Just a castle as production building should be enough, you can grind away the town defenses with conquistadors and petards as you please.