Here’s the thing. Classic Fire Emblem is pretty well known for the one key trait of the series. When units die in battle, they die. Dead is dead. They aren’t coming back if they’re killed in combat. Or if they are a major character they will take too serious of injuries to keep fighting in direct battle.
Newer Fire Emblem allows the option of playing on classic or casual. Casual let’s you get units back after chapters so you don’t need to worry about someone being killed off forever.
I still remember beating hard mode on Heroes of Shadow without losing any units and that’s one of the older games, so even so it’s definitely do able.
Some quick things:
It’s a perfectly viable method to just skirt the edges of the enemy range and then have faster units pull back to trigger the aggro range of enemy units and draw them into your own unit groups. Don’t be afraid to have about three units attack a single target, the enemy will have no problem doing it if you get surrounded.
Pegasus Knights make excellent mage killers and can fly over pretty much all terrain. They are hopeless against archer types, but archers can only attack if their enemy is at least two squares away. It’s possible for a PK to swoop in right into their melee range and off them without any damage.
Healer units get exp for…healing. The trick to this is that unlike combat units it means they don’t have the same requirements for getting exp. They just need to heal, so you can level them up pretty quick just by having them heal 1 or 2 points of damage while standing behind a unit.
Enemies will almost always go for the unit with the lowest hp in range. Usually this is mages, thieves, and healers and archers by default. They will look at the ones that are easiest to drop in one round without being able to hurt them so they will often attack archers and healers. This can actually be used against them when your back is in the wall to have more damaging units survive a round.
Part of it is because the one who attacks a unit first will be given the first move in battle and scores the first blow. Really important because enemies are allowed to counterattack after. It’s possible to kill enemies with a counter and for them to do this to you. If you can one shot their squishest units in the first move of the first round, it’s generally for the best.
FE loves stationary bosses that stand over the seize point. They won’t move until someone gets in their aggro range which is generally short. More often than not, they will refuse to leave the seize spot. This however, gives you plenty of time to get all your units in place and attack the boss as a group since they won’t bother moving.
Reinforcements from enemies WILL happen. This can be a problem when they end up right behind you. But…if you have a unit standing directly on top of a staircase or a fort that reinforcing spot is “sealed” and no new enemies will spawn from that spot. Just be careful of how many spawn spots there are because if you don’t have enough people to seal them all, it could risk getting units killed if they get swarmed by other reinforcement groups.
Highlighting enemies let’s you see their movement range. This is really useful to know and helps judge what to do next.
I know this is a long post, but if you can grasp these things, than most of the games will be fairly manageable.