Trails in the Battlefield

Turn-based battle systems are pretty much as old as role-playing video games themselves, and still holds an important place among gameplay mechanics with their unique strengths and weaknesses. This article will examine these unique qualities while looking at Trails in the Sky series in-depth, how well the games play into the system's strengths and avoid its pitfalls. Please note that I will mostly talk about First Chapter and  Second Chapter here, as I didn't finish The Third yet.

The Battle Rhythm

Obviously turn-based battles can't feel intense or fast like an action battle, but such a direct comparison misses that turn-based systems have a rhythm of their own, at least they should be. Most design improvements on turn based battling have been about creating and fine-tuning a unique rhythm. So, let's look at how this rhythm is created and maintained in Trails in the Sky games.

• Fast transitions: As soon as we crash into an enemy the battle starts, no long whoosh effects, no long introductions. Quitting battles is easy the same way. Just a short victory pose then statistics slide in, then the battle ends. And thanks to coming out to PC more than ten years ago, loading times are almost non-existent, controls and menus are responsive and smooth. While being a technical issue rather than design, loading times can really render a turn-based game unplayable, as seen in infamous PS1 port of Final Fantasy 6.
• Quick moves: Battles themselves are quick as entering them. No normal move, whether enemy's or yours, take more than 2-3 seconds, even special moves take 10-20 seconds at best, and in later versions of the game they are even skipable! Furthermore, battle animations feel smooth and lively. Although unskipable absurdly elaborate moves has their own charm, a good battle rhythm is definitely invaluable.
• Losing battles and loading is easy: Long game over sequences are real pace-brakers, and while this might be beneficial sometimes, it kills the rhythm when you have a high amount of short battles and sadly it still is very common in famous turn based RPGs. Trails in The Sky on the other hand has a 3-seconds of game over screen which is followed by an option to restart the battle or loading an old save! If player wants to take a break and reflect, they can do that as long as they wish, and start battling as soon as they want! Additionally, you can save and load anywhere you want and very few enemies have more than one form, making the game both very humane and much easier to pick up, despite it's very high amount of dialogue.
• Battles are fair and right amount of challenging: You can see the order of moves and how many turns a move will cost in a sidebar. You can also see when a luck based event will happen, such as critical hit or HP restore. You can manipulate your luck by timing yourself correctly or bypassing the move order with your special moves! You can see enemy's elemental weaknesses easily and unlike a lot of RPGs, using bad status moves is highly encouraged and you have a fair chance of preparing against enemies' bad status moves. You can access all information regarding battles with an in-game guide. Healing is not very difficult and game makes you aware when an important battle is close. All of these feature ensures bad surprises rarely screw you over and combined the easy loading, it really takes a lot of chore out of difficult battles. 
• Lack of Hit Sponges: Even in higher difficulties you will rarely have a "Die already!" moment, you are sometimes even encouraged to finish enemies as soon as possible, not by an external timer but through the design of enemies themselves. This is one of the things that can go unappreciated unless you experience hit sponges yourself, such as more than a few enemies in Final Fantasy 10, and all story bosses in Persona 4.
• Good Level Design: While some dungeons are fairly maze-like, most of them are kinda simple. But this simplicity adds to the rhythm of the game. You can see the enemies on-screen allowing you to ambush or bypass them as you like. You have a decent moving speed and dungeons never overstay their welcome,  especially large dungeons have adequate warp systems and you can usually retreat from dungeons fairly easily.
• Easy Grinding: The amount of experience you get scales inversely with your level, which means lower-level characters will level up easily and you will be soft-blocked at certain point, which gives you a nice indication whether you are good enough to fight the next boss. Money and items will be just in right amount as well, you will get valuable items while exploring the dungeon and if you fight enemies at a normal pace, you are quite ready for the important fights. Grinding is even easier with specific hard-to-defeat monsters giving you absurd amount of experience and sepith(the stones you get your magic from). Even in very high difficulties, you will rarely need to walk around just to level up more.
• Music: As I analyzed in-depth here, the music in this game, adds so much to the rhythm of the battles. For a negative example, we can look at Final Fantasy 10, where while a good track, main battle theme just feels too grand and starts to wear on you for the quick encounters game wants, and despite vivid and lively animations, the battles feel too slow.

Of course, with regards to the battle rhythm, you can also take a complete opposite approach. You may want to make sure every enemy encounter feels memorable, battles are slow and methodic, and player is open to bad surprises, but you will only have a few dozen battles over the course of the game.  This approach is used frequently in tabletop-based RPGs. Dynamic frequent battles and methodic sporadic battles both work very well, depending on the game but please commit to one of them fully.
The only potentially pace-breaking element might be Craft Points. They are used for character specific moves and high damaging special moves. Unlike health and magic however, CP doesn't easily filled by healing. Instead it is mainly filled by attacking and getting hit, which nudges people to fight and grind, and is fairly well at it too, but it ended making avoid using CP outside of boss battles most of the times. Thankfully, as series went on, more ways of restoring CP was introduced.

Versatility, Tactics and Challenge

Turn based battle system allows you to simply focus on thinking, you can easily turn battles into puzzles and create deep system involving a lot of numbers. The pitfall here is it can be either too complicated to the point of requiring material outside of the game, or the game might be too simple that simply using your greatest attack and occasional healing are only things you do entire game. (Pokémon is a marvelous example of falling into both pitfalls at the same time.) Of course, how challenges and how complex your system should be depends a lot what type of rhythm you want your system have.
In Trails In the Sky, you have three type of moves; default attack(which is not a throwaway), Crafts, skills that are unique to character and Arts, modular magic spells similar of Materia in Final Fantasy 7. Although characters have different limitations on what type of Arts they can use, the system achieves both giving players a lot of options and making every character feel truly unique.
Arts themselves are interesting because unlike most games, high-sepith magic doesn't usually result in higher damage, it increases the area of spells and gives different status effects. This means the fireball spell from the beginning of the game is often just as useful against late game bosses. Early Crafts too, usually don't become useless as time goes on. So, pretty much you are compelled to think about utility vs. cost whenever you are using a spell. When the time cost also enters the equation, especially boss battles selecting which moves to make isn't a trivial question. You also really don't have huge attacks that destroys bosses in several hits, you need to be efficient in your resources, using status effects actively is encouraged.  The system overall works very well except in three cases.

1. Some spells aren't just worth it. They are improved or just removed all together as the series went on.
2. "The Earth Wall" spell might be broken. You see, it's a spell that makes all of your characters under a small area immune to one attack, any kind of attack.  On the one hand, If you can be fast enough, you can just spam that spell and make even the most terrifying enemies unthreatening. On the other hand, if you don't use that spell some bosses might be really difficult, especially on higher difficulties. The designers knew how to get around that spell and some fights are still hard with that spell too, but it can make a non-trivial amount bosses a cakewalk. Yes, they improved on this too.
3. Chain crafts don't work. It's a system that allows more than one character to attack at the same. It's cost is too high to be actually useful. It looks like the prototype of a similar and better system that was used in the later games.

Overall, I would say in terms of difficulty, First Chapter is alright, Second Chapter is challenging, especially if you go for full completion. Third is from what I have played so far, might be the hardest Trails games and one of the most difficult JRPGs I have played, designers went really all out to test the player, however the game is still pretty fair. Most importantly all three games just feel good to overcome, it's one of the few games that made me want to go for the hardest difficulty.

Abstraction

Now, let's think about what we are actually doing in turn based battles: We can use swords, bows, machine guns, football ball, baseball bat, chair... We may fight against wolves, enemy warriors, zombies, mythical monsters, deities, manifestation of emotions, houses, pots, pirate ships, toys, cacti... We can also utilize things like elemental magic, psychic powers, can summon planes to blast the entire area, throw cookies that hit way too much damage, can simply withstand planet destroying attacks... 
What I am getting at here is reminding you how outright bizarre can turn-based battling can be and how well we all accept this. Even today, it is incredibly difficult and hardware-demanding to simply develop a real-time battle system that can allow such events, and impossible to looking outright absurd while doing it. This is the price of being highly visceral, we want to feel like we are in the battle. Turn-based battles can instead simply hide in abstraction, despite the graphical quality, it can simply leave the messy details to the player's imagination.
A good example of the stark difference in perspective can be seen in Elder Scrolls 3: Morrowind. You can attack from first person perspective but still may miss your attacks despite visually hitting the target. "Missing belongs to a tabletop RPG", players often say when complaining about Morrowind, they exactly mean such abstractions belong to a turn based(or at least a pausable real-time) battle system.

For JRPGs, Trails in The Sky games are surprisingly down to earth. While especially Special Crafts can give a nice spectacle, neither you or your enemies are too absurd. The well balance the games have allows them to achieve something often misses from JRPGs.

Integration into Setting and Narrative.

It is often said that turn-based battles simply feel too detached from the story. Although it is not true that the designers don't try to mitigate or circumvent this, it's not a unvarranted criticism either. Abstraction, when mishandled, can become a great pitfall from the games, it might make player feel like battles don't have a presence in the game world.
Games have different ways to avoid this pitfall: In Shin Megami Tensei games, battles are often set in partially or entirely fictional worlds that has necessary conditions to be able manifest them. Final Fantasy 4 have humble enough battles that make sense for their worlds. In Undertale, everything is so well-integrated that even abstraction make sense.
In Trails in The Sky series, characters sometimes use Arts and Crafts outside of cut scenes and act like they would in battles. This is such a small but effective measure to make battles part of the universe. In Trails universe, it's totally natural that people gain powers like jumping several meters in the air to cut the enemy just by training, just as natural as they have hair colors like purple. And its magic has an already important place in the lore.
This makes establishing narrative place of battles quite easier. Young adventurers as protagonists is a well-known RPG cliché, but it is a cliche for a good reason. It's a safe but sure way to ensure characters have energy, free time and reason to fight so many random monsters and leveling up to have narrative weight. In Trails in the Sky games, your protagonists are not only young adventurers but they are also trying to become a part of an organization which composed of adventurers defeating monsters and protecting people.
A good example of failing at this is Final Fantasy 10. The battles and story are really neatly completely separated outside of story battles, almost nothing that happens in battles has a weight in setting(Except in the style - For example Wakka using a Blitzball ball because he plays Blitzball) Having random battles, leveling up, various mini games, secret bosses, item hunting have nothing to the story of going on a tragic pilgrimage to stop the impending apocalypse. As much as I love RPGs and turn based battling, I have to say Final Fantasy 10 might have worked even better as a non RPG.
Is this really that important? Yes it is, even outside of me being a huge nerd, it is important. The mistakes in Final Fantasy 10's design are standard practices in AAA games now. Look at yearly big-title releases. They all have to have "RPG mechanics", you need to have "content". So much content, so many mechanics, "so much thing to do", like a kitchen sink. Indie games on the other hand keep reminding us well-focused design is important and how well games can be when every part of the game works in harmony. The difference in design perspective are the reason I tried to complete every quest the Trails in The Sky series and bypassed most of the side content in 3D Final Fantasy games.
No game mechanic should be added to a game, without a clear objective and consideration of how well they integrate into the other parts of the game. And turn based battle systems should be approached with this seriousness, because they can achieve much more than being "the thing you put when you make a handheld or mobile RPG".
(screenshots mine)