The natural process of eliminating a group for certain reason. Sometimes wars are fought to protect a group of people, to obtain land and wealth. Wars have ALWAYS been fought. A war is not just a conflict between two militaries. There are many different wars, such as gang wars. There will NEVER be peace, so get over this fantasy idea that there will be. Wars were fought thousands of years ago, they aren't new. If all the weapons were destroyed people would go back to using fists and rocks and wood to wage wars.
Japan attacked Pearl Habour and the United States dropped a nuclear bomb on hiroshima and nagasaki.