Nan Yanoi is the stronghold for the Tau Empire forces and honestly it can be a bit of a tougher one.
You start out without a base in the south east section of the map, but with some additional forces along with your Honor Guard. You have to move to the north, fighting as you go, to destroy a smaller Tau base and take over the area. Once you destroy all of the buildings there you will be given a primary Stronghold building and some builders, allowing you to finally start building up your forces. Now the main grind begins.
There are several bases scattered around the map with one big main one at the north west, and you have to destroy the Coalition Center at the middle of that north west base to win. There is also a count-down timer; the Tau will receive heavy reinforcements from their fleet after a period of time. The fleet is being guided by three beacons that are in bases on the eastern section of the map. Destroying the first two will delay the reinforcements, destroying the final one will halt them entirely. Also, the Ark-Ka cannon emplacement is in the middle of the map and will periodically fire an anti-infantry blast at your forces, even if they are in the middle of your base. It's not VERY strong, your main infantry will be able to survive a couple of hits, but this is still draining. However, you can take control of this cannon yourself and use it against the Tau forces if you take control of the Critical Location point next to the cannon.
Also, if you are playing a race that has air units that are good against buildings, unlike most other strongholds it is NOT recommended to use them to do quick raids to take out vital buildings; not only is nearly every Tau base protected by at least a couple of Barracudas that are quite respectable at anti-air combat, every base has multiple entrenched Broadside Battlesuits spread throughout them especially the northwest main base. These guys will do ruinous damage to your air units no matter where you try to attack from, and since they are infantry the air units that are good against buildings are terrible against them. Even a full squad of five anti-building air units won't get very far in an attack, so you shouldn't waste the resources.
Those Broadside Battlesuits, in numbers that any Tau player will envy, will still do quite hefty damage to your ground forces including infantry, and since you want to stay ahead of the fleet reinforcements you'll have to be quite aggressive in your attacks. Expect to take a regular stream of losses as you grind through the bases towards the northwest.
It is highly recommended to have both at least a couple of strong melee squads and a number of units with long-range infantry disruption abilities preferably by knockdown. You don't want the Fire Warriors staying on their feet letting rip at your infantry if you can avoid it, so while your main attack infantry is focusing in one area try to disrupt the Fire Warriors elsewhere to cut down their firepower.