Let's leave the 'war' part for now :-p
And in love, well, loving each other is not enough. It may be the beginning AND the end, but there's a lot in between. Trust, for example. And this 'taken-forgranted' trust (or the lack of it) often decides the shape of a relationship.
It's all rosy in the beginning. Thing is, we don't care! It doesn't matter what the other person is doing. Or WHY. But as things move on, this 'why' becomes the most-used word in couples. Why didn't you call me? Why did you get late? Why didn't you let me know? Why're you talking to me like this? Why do you go to that restaurant? Why do you wear that? Why do you talk to XYZ? Why don't you like talking about ABC? Why don't you shave? Why do you watch that stupid channel? And so on and so forth. For every why there's a counter-why. And neither partner lets the other remain 'why-less' for long. And most of the time, it doesn't even mean anything. Most of the time, the question is irrelevant. It's the tone that tells the story.
And that brings us to another highly used tool in love. Sarcasm. Actually, it's as beautiful as it is intricate. It's not like a missile that'll go 'boom' and destroy everything, it's like burning coal that'll burn your hand - slowly - and hurt till it turns itself into ashes. And maybe that's why - it's mostly the weapon of guys (like crying is of girls ;) ).
In fact, people in relationships (both guys and girls) have even confessed to getting pleasure out of hurting their partners. "Just wanted to ensure I could still hurt you!" Ha, Nice! And it's not sadism, just "I'm still the boss" feeling.
Gee, I'm on the wrong track :D Am feeling like a 'Love Guru' :D Will post it anyway! :) And here's a link, just for fun ;)