How Do I Write A War?

During the climax of my chronicles of fanfiction, there is a massive war. Armies of Pokemon clash with both sides having 'King Pokemon' and one or two very minor legendaries (Shaymin will appear as a healer maybe). How will I show this immense battle with Titans clashing and Pokemon fighting? Should I switch point of views or stick to the main character?

Some background information. King Pokemon are massive (bigger than normal) Pokemon, most of which are constantly mega evolved. They are usually the leaders of factions within the type and are placed among the legendary Pokemon. There are also no Pokemon trainers as this is a fanfic set before the events of PMD, way in the past.

Can someone give me tips or anything?

Hm, perhaps look up some clips/scenes from movies? Since you're going for Pokemon clashing, go for fantasy ones like Chronicles of Narnia or Lord of the Rings for instance. With whether switching point of view or keep to main character, sticking to one point of view might be easier but if you're confident enough you can go for different points of view. In the Song of Ice and Fire novels, in the second book there was a battle going on and George RR Martin wrote the battle in several points of view, both in the battlefield and those inside the castle. Perhaps you can go with that route (you said no Pokemon trainers, but maybe other Pokemon are doing something else besides fighting).

A Pokemon war? Sounds interesting. Usually within a story, there is a theme, or a deeper concept. The armies will usually represent different views of the argument; and the focus usually isn't on the battle itself, but typically on the leaders who we know more about. (or maybe the POV is one of the grunts)

I think that the build up to the battle is just as important as the battle itself. While this may seem obvious, consider the following:
Why is the battle happening?
What does each side have at stake?
What is an absolutely unacceptable loss for each side?
How does each sides people feel about the war?
What is the setting of the battle? Why does the battle happen at the selected location?

Historically, battles would often happen in
Open fields (Enables the greatest use of traditional flanking tactics)
Hills (For when side is attacking another, the hills provide a terrific defensive advantage. Also, ambushes)
Forests (Especially in closer to Modern times, given the number of forests the U.S. was in during war. forests provide natural cover against ranged attacks)

Additionally, realize that each Army will likely be divided into different groups, or divisions, based on their function.
Infantry (Ground based pokemon) The main ground unit of an army.
Artillery (Long ranged Pokemon. Anything from small attacks (kinda like bow and arrow in real life) to large attacks (like cannon balls). Artillery timing is fairly complicated;
whether they are firing at will (as soon as they can) or in barrages (everyone shoots at the same moment). Well timed barrages can be devasting, either softening up the opposing army line, or shattering an enemy attack.
Flying Divisions/Particularly fast pokemon - In real life would be cavalry, or air assets - These are great at running disruptions; hitting the enemy where they are weak.

In battles, flanking an enemy, and also having the high ground are two of the biggest factors to strategically winning a battle. When Flanked, an enemy is attacked on more than one side, which leads to chaos. It's very hard to defend against enemies from two directions. Additionally, when an enemy has to go up high ground, they will be tired; which is a serious disadvantage.

Since we have pokemon though, we can get far more creative.

Water pokemon could turn the ground into mud; Pokemon stuck in mud would be slow; perfect for artillery units to destroy.
Fire Pokemon could light the area on fire; burning the enemy out, creating large smokescreens (which way is the wind blowing?) that not only obscure a target, but if thick
enough would cause them to choke; which would be really disruptive.
Flying pokemon can drop in batches of ground units, kind of like paratroopers dropping.

Additionally, given how significant type advantage is in battle, divisions would also have to strongly consider type advantage. Artillery may have electric types, especially to deal with an enemy flying division.

A heavy fog could help an army sneak up on the enemy without being noticed. If your army is obscured by woods, fog, smoke, nighttime, heavy rain, etc, then enemy artillery will have a hard time effectively shooting at them. So if I had mostly infantry, I would try to sneak attack an army with tons of artillery a) when they least expect it b) during horrible weather, and preferably at night so they would have the least chance of hitting.

And on and on and on.

Just don't forget! There is typically a larger conflict in terms of the theme that is stake in the story, and you can't forget about it! If you lose sight, you may have an awesome battle, but the story could suffer for it.

Happy writing!

One of my fanfics is centred around a war. It mainly focuses on the world under effect by it, but towards the end I wrote a large battle scene. I personally changed point of view from each of the main characters involved in the battle and wrote it that way. You have to remember the noise which could be going on, being trampled or bumped into even by members of your own side, the fact that war is a terrible thing and in battle there can be significant losses.

I second the suggestion to watch battle scenes. They can be hard to describe when there is so much going on. Some of the descriptions could be confused when the character(s) are overwhelmed with numbers?