Battle in Bulgar (ブルガルの攻防 Burugaru no Kōbō lit. The Offense and Defense of Bulgar) is Chapter 19B of Fire Emblem: The Binding Blade if you take the Sacaen route (which happens if by the end of Chapter 16, the experience points gained by Sue and Sin were more than or equal to that of Shanna and Thea).
The 5 red houses act like villages and give you the items:
Note: this entry is incomplete. Please add to it if you have more information (these reinforcements are relative to Hard Mode, they may be incorrect for Normal Mode)
- Turn 8: 4 Level 17 Nomads with Short Bows from southwest, 4 Level 17 Wyvern Riders with Steel Lances from southeast
- Turn 10: 2 Level 17 Dragon Knights with Steel Lances from southeast
- Turn 13: 2 Level 17 Nomads with Short Bows from southwest
- Turn 15: 2 Level 17 Dragon Knights with Steel Lances from southeast; 4 Level 18 Myrmidons from various houses within the city (2 with Steel Swords from the center, 1 with Armorslayer from northwest, 1 with Lancereaver from northeast)
- Turn 17: 4 Level 18 myrmidons from various houses, same distribution as above
- Turn 18: Level 17 2 Nomads with Short Bows from southwest; 4 Level 18 myrmidons from various houses, same distribution as above
- Turn 19: 4 Level 18 myrmidons from various houses, same distribution as above
- Turn 20: 2 Level 17 Dragon Knights with Steel Lances from southeast
- Turn 23: 2 Level 17 Nomads with Short Bows from southwest
- Note: this entry is incomplete. Please add to it if you have more information.
There are three ways into the city. Two parts of the wall can be broken near the starting locations of the enemy Wyvern Riders. If you can quickly dispatch the small amount of hostile forces outside the gates, breaking these should prove to be the fastest way inside.
It is important to note that most forces inside the city will start moving towards you as soon as an entrance is made, so a highly evasive or defensive unit should be placed at the front of your first entry force. Both walls have 100 health, but using Eclipse can help destroy them in only two attacks.
The enemy Sages hold a Sleep and a Silence staff, so bringing a Restore staff of your own can be beneficial.
The tool tip for the main gate labels it as a Door, but neither thieves nor the Unlock staff can open it. After around 12 turns, however, the gate will be opened, meaning you can sweep the outside enemy reinforcements and bait out the long range spells before this happens. It is possible to have (part of) your forces wait for the gate to open while taking out the enemy reinforcements.
If you don't plan on rushing the inner area it may be a good idea to choke the gate with some 1-2 range tank units, preferably some with good speed and avoid. Make sure you keep them in range of their support partners. Good examples of this would be a well trained Allen and Lance with Javelins. You should be able to deal with the wyvern and nomad reinforcements if you are prepared for them since they spawn with relatively basic weaponry, only 2 at a time, and each group comes staggered from each other.
In Turn 13, the boss will order the destruction of the rebel 'villages' inside the walls. (edit: This may be a translation error? If you read this line and thought that the enemy was going to pillage the 'villages' you need not fear, since I don't think even given no player units in their attack ranges that the enemy will pillage the villages. I killed no enemies inside the wall before this line and none of the villages got pillaged, but this might be unique to my playthrough and if anyone has experiences will the enemy pillaging the villages correct this, but otherwise you should be free to visit the villages at your own rate)
The boss, Gel, is a Swordmaster with a Light Brand. If you are worried about his critical strikes, only fight from a distance to remove the risk. Fully abuse both combat triangles against him, using Anima magic from a distance and lances from up close to increase your accuracy against him. So long as you can hit, he should fall easily.