How does the tactics trainer work in Fire Emblem Warriors: Three Hopes?

In Fire Emblem Warriors: Three Hopes, you’ll help run a camp for one of the game’s three main armies. The camp will expand as you continue playing the game, and new facilities and features will be added. Eventually, you unlock facilities that contain special NPCs known as trainers or masters. These trainers offer you a special service to help improve certain aspects of your army. For example, The Training Instructor allows members of your army to increase their class level. But what is the purpose of the tactics teacher in Three Hopes?
How does the tactics trainer work in Fire Emblem Warriors: Three Hopes?
How do I unlock Tactics Academy and Tactics Instructor?

The Tactics Instructor is located in the Tactics Academy, which is only unlocked at the beginning of Chapter 6, Bridge of Betrayal. The Tactics Academy is a classroom and the Tactics Instructor is in the back of the room in front of a blackboard. The tactics trainer offers to improve skills and teach members of your army new tactics, including increasing the warrior gauges of all your characters. However, you must first expand the Tactics Academy to explore basic multi-opponent combat. You should have obtained the necessary material to upgrade the academy to the basic level, which is a basic 10-beginner combat manual.
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What can the tactics teacher teach?

Without a byleth to teach all of his students all the important parts of war, the generic tactics teacher is about as good as you can get. The Tactics Instructor is able to teach all members of your army a variety of new tactics. By expanding the facility to the Research Basic Multi-Opponent Battle Tactics, the instructor can increase the warrior gauge for all members of your army. This gives your characters an extra bar of Warrior Gauge during battle, and we highly recommend increasing the Warrior Gauge on all characters you recruit.
Using the Tactics Instructor does not cost any Activity Points, but it does cost money when the Instructor teaches your army a new tactic. How much money it costs depends on what tactics you teach your character. For example, it costs him 500 to increase the warrior gauge for a single character. You can select more than one session at a time by pressing the Group Session + button. You can also remove individual units from the selection if you wish.
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Certain characters can learn some tactics that others cannot. Characters with crests can learn tactics that increase crest level. The main tactics most characters can learn are listed below:
- Increase Warrior Gauges (Lv. 1 – 2)
- Upgrade Unique Action Skill (Lv. 1 — 2)
- Enhance Unique Support Ability (Lv. 1 — 2)
- Enhance Unique Tactical Skill (Lv. 1 — 2)
- Research new recovery items (Lv. 1 – 2)
- Increase the use of Recovery Items (Lv. 1 – 3)
- Increase Skill Slots (Lv. 1 — 3)
- Increase Crest Level (Lv. 1 — 2)
How do I learn more tactics?

You can only teach all your players the Tier 1 Increase Warrior Gauge Tactic after completing the first Tactic Academy expansion. All other tactics are locked until you continue to upgrade the facility, with specific upgrades unlocking specific tactics. For example, you need to upgrade the facility’s Research Medical Arts to unlock the Research New Recovery Item tactic. You need the basic building material to unlock the basics of the facilities. In order to further develop the basics, you need high-quality building materials, a standard combat manual, an elaborate building material and an advanced combat manual.
https://www.gamepur.com/guides/how-does-the-tactics-instructor-work-in-fire-emblem-warriors-three-hopes How does the tactics trainer work in Fire Emblem Warriors: Three Hopes?