Fire Emblem: Shadow Dragon/Chapter 12X

Before Chapter 12X
In Chapter 7, just beat it normal. Just remember that you can't recruit Minerva yet. Also watch for the reinforcements in the south forts.

In Chapter 8, you get those weak units at the start. Do the normal, dispose of them. Roger, the recruitable knight, isn't necessary. Watch the reinforcements at the top. Also remember to buy some stuff from the shop.

In Chapter 9, you get the sniper (or you could just let the thief kill the village). Get rid of him also...and any other useless unit you may have still. Remember to get the treasure and watch out for the sheer number of enemies.

In Chapter 10, just play normally. Get your first Master Seal and then recruit and keep (optional) Minerva. I personally dislike her in favor of a promoted Shiida. Anyhow, just watch for the main army's advance. Get rid of Maria also.

In Chapter 11, remember to watch for the ballistas. Recruit Linde. Use her if you want, I don't like her in favor of Merric. Remember that the manakete is unrecruitable. Also remember that Jake can be recruited, but Beck is a better choice. Other than that, just watch the ballistas.

In Chapter 12, all the units in the jail are pretty much useless. Let them die so you don't have to worry about accidentally leaving them alive. Note that the next gaiden chapter is after this. Therefore, make sure you have less than 15 characters left. Also remember to use a thief to get the chests.

Time for the second gaiden!

A Traitor's Worth [CHPD1]
"After taking back the palace, the League rode across Akaneia, freeing the greater part of the kingdom as they went- all except the west. A landed knight there named Horace, who had betrayed Akaneia, to join Doluna, continued to stubbornly hold out against Marth's forces. Nyna could not fathom why such a fiercely loyal knight would turn to treachery, but with her other knights calling for Horace's blood, she had no choice but to give in and ask Marth to bring the traitor to justice."

Preparation
This battle is pretty linear, there are two villages to visit. When you begin the map, Dejanira will approach Horace into dialogue.

Begin
First turn, kill the two immediate enemies then move your WHOLE army to the right. In order to recruit Horace, you must beat the chapter without killing him. Don't worry...

After you finish your first turn, dialogue moves to the enemies.

This means that the whole middle section of enemies won't attack unless you do. Sounds good if you want to recruit Horace, just sneak up the right and beat the boss.

Note that the easy way to see if an unit will not attack is see if they are from Grust or Akaneia. If Akaneia, they won't attack. If Grust, they will.

The enemies along the way aren't anything special. Three mages will rush from the north, but they are easy enough. Check out the villages with Marth though.

First one...

Move along up, kill manakete then visit the second village...

Now, just move the units in to kill the boss...some pirate reinforcements should spawn in the west first though.

Note that if done properly, the pirate reinforcements shouldn't even have caused a problem. Of course, you could kill them for experience or you could just seize the gate.

Upon seizing the gate...(and without killing Horace)

End of gaiden chapter. Next one is Chapter 17x by the way.