It's commonly believed that wars are source of many bad things.
However they still bursts into and goes on.
What are causes?
First and foremost source of wars is economy.
There is huge arms industry.
In addition often winner take natural resources as oil, gas and so forth.
Other source of wars are historic events.
For example my country has territories which was German through many ages.
On the other hand Lithuania's territories was Polish through hundreds years.
It can be cause of conflicts.
There are often civil wars, when in one country are different religions, nationalities, tribes or enemies parties.
Wars change lives of millions people.
The worst consequences is: dead, wounds, disabilities.
People stay homeless, hungry and without the good future.
They have to desert their houses and look for luck in others countries.