Existence of Discords

In this universe of unity, why must there be so much discord and so many wars? Has the memory of all the horrific wars throughout history faded? Did humankind forget how they lost their strength, force and dynamism during the seven-year, thirty-year, and hundred-year wars and two massive world wars? Did they forget how they lost their resources, powers, and dynamism and pursued continuous animosity with their enemies, instead of progression? If we turn the pages of history, if we read the history of all nations, and if we extract statistics from them, are we going to see anything but wars, bloodshed, animosity, destruction and execution in them? Strangely enough, they consider this as a badge of honor, and one who became triumphant with such coercions considered himself victorious and successful. Is this not surprising?