^Though at the same time, war would still be fought without religion. Humanity as a species will always wage war upon itself, and will always find ways to do it. Even if there is no religion.
Al Qaida warps religious teachings to convince their followers that what they are doing (trying to destroy Western civilization) is justifiable. Because religion is something of passion to many people. Are people too passionate about religion? Probably. But religion is only one piece of the puzzle. Fresh water on this planet is going to in the coming years become more valuable than maybe even oil, if this keeps up. We are using more freshwater than the planet is capable of replenishing, and water shortages are already happening. The Israel/Palestinian conflict and many other territorial wars in the Middle East and other dry areas would *seem* to be all about religion, but in reality, fresh water and control of those water sources is also a big part of it. A huge part of it, in fact. Portrayed as a lesser part of it, because it's harder to work your people into a passionate mood over something like water versus religion, which is a much more personal subject.
It's the same with anything....Invading Iraq to wipe out "a dictator who mistreats and kills his own people and possesses weapons of mass destruction" is much more convincing to the American public than "look, without oil, our country and the rest of the free world will die, it's that simple. We can not exist without it. Saddam Hussein is sitting on top of oil and he can at any time cut off a large supply of oil to the free world, he needs to be gotten rid of."
It's not as powerful. France going into Libya and demanding the rest of the world do the same thing is ....well, they get a pretty big piece of their their oil supply from Libya. That dictator ruling the nation was unstable, and this could in the future affect France's ability to get this oil. Their main concern was not simply for the lives of the oppressed people of the country, which they said it was, but mostly their oil supply. But what's more convincing to the world? Bringing emotional weight into it. (Which is actually pretty hilarious because they yelled at us for doing the same thing by going into Iraq, and refused to help, when, then, years later, they demand our help to go into Libya for the exact same reasons. But that's another topic.)
People will always find ways to use "emotion" to manipulate others. Emotion's both the strength and weakness of humans. Religion is a source of passion and emotion for many people, and so it's constantly used to justify conflict.
Simply put, though, there are many reasons as to why people fight. Religion is just one reason.
(and yeah I'm aware I got awfully deep there.
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