What lead to wars in the past?

Answer 1

Most wars have been caused by territorial disputes of some kind. Two different nations (or tribes, empires, cities, etc.) claim the same piece of land, so they fight over it. There have also been lots of wars which have resulted from more than one person claiming to be the rightful ruler of some nation or other political entity. People then pick sides and fight about it. Many wars have also been religiously motivated. Religions are known to try to impose themselves upon people and to stamp out the practice of competing religions. This is still happening today, particularly the conflict between Sunni Islam and Shia Islam, but many other conflicts as well.