What Lily_j means, is that in a utopian society where there is no arguing or hate and everyone on Earth could coexist as equals, then war is unimportant (for the reasons she listed). However, we are extremely far from this scenario, and as such, countries are put into situations where they must defend their people, cultures, and laws or others will try and take control and change them for their own benefit. Without war, countries like America would exist in a state of fear and turmoil. The destructive power we possess is what keeps other countries from inflicting harm upon us. And if they do inflict (or even attempt to inflict) any harm, and if we do not retaliate, they will continue to do so. In our world, without war, you cannot have peace.
War is essential to our future, and may also potentially destory us; a sort of love hate thing is way I see it.
Look at the launch of Apollo 11, the only reason why America got the moon so fast was competition with the Soviets, most of our technology either for recreation, industry and other areas were technology is developing is only doing so due to advancements in military technology. What reason does man have to develop fast, if there is no immediate threat, and it's the same way with evolution; a species will only develop throuch thousands of generations of random mutations due to constantly being challanged. But if don't agree that think about it like this, no matter waht war will happen, even if it's a thousands years from now with some alien species of Singing Chickens. :)
Actually, on the contrary, war is very unimportant. War makes no contribution in bringing peace to the world. It also does not make nations stronger and does not even contribute to the social and economic development.
War causes countries to go way beyond their current economic and social position. It causes generations of people to suffer. Hundreds of people are killed, and more than those are injured. It causes military deaths as well as civilian deaths. The atrocities of the victorious nations causes mental and physical problems in the people especially women and children. So by no means war is important. It is better if countries take the route of dialog and understand each other's situation.
