I am not sure if I may post this here, but I was writing a (short) fantasy story. 
It is about a conductor who lives in a culture where music is used as a weapon. Since it is fantasy, there are some battles and wars to be fought, although the war is where I got stuck at the moment.

What do you think makes a war between two armies exiting to read about?

The fight will take place in a 'counrty' which has a good relationship with both fighting counries and is thus sort of neutral, but attacked along the way. The weapons of both fighting countries are not defined yet, but the neutral nation uses the music and longswords.

Also, if you want to read the first part of the story, I have a link to it on the Nexus. Any other comments or tips are very much appreciated :)

Well I've found that most people get more into the war when they know who's who and know where they already stand (Given that they know what side the story is from.) ((World War II for example.))
People also enjoy it when they have build up. Like if a novel leads to the war, if people know the politics and players they can really get into what's happening and know why the fighting is happening.
If people are just thrown into the war from the start of the story and it isn't something they are familiar with they can handle it but aren't into it as much.
 

Thanks, Friðr Loðbrók.

The main difficulty I now have is that the side the story is viewed from, wants to prevent the war at all costs, and hasn't chosen sides yet, and doesn't want to choose either.
In the end, they have to fight. One of the war-faring nations will attack. 
I know that this can bring some tension, but I am not sure how to do that in the story....

An ancient lesson of describing a battle is to switch senses every so often. Sight, sound, smell, the taste of blood, the nasty sting of breaking a bone... This is a standard feature for the likes of Tolkien, Martin and everyone in between.

Are you going to write the battles in music theory? I would love such a novel approach. Now that I think of it, let me try!

"He heard the (foreign army) trumpet wing raise a wailing tritone that sunk into the right flank, taking a dozen men. Still staggered, (notable warrior character) yanked the battleflute from his torn quiver and sent a diminished second at an enemy centurion. The officer tumbled backward, but managed to grasp his dented shortharp for a hasty arpeggio that settled to the dominant. (character) cursed. The lines were turning into a dissonant wasteland left and right.

Suddenly the booming voice of the tuba wagons returned, but it was sweeping aimlessly, felling friend and foe alike, and one of the bells had clearly been hammered apart..."

Nice one, Freymulaar!
I am not that familiar with hardcore music theory. It's a bit more basic ;) You could really write one though!

I'm afraid mine is a bit more boring than that... I have a few devastating instruments (a horn which causes earthquakes and landslides, sounds which make people sick or things that focus sound to one person (those actually exist)) but apart from that it is the melody which has the effect...
I want to try and write a few songs myself, but I should practise a bit on it :)

And yes, I will keep the main character consious throughout the big fight and use the tip about the senses. Good idea.