The Sunni-Shiia "war" is still a very existing fact in our world today. Due to different interpretations of the holy book, they are having different opinions and this leads to violence between both genres.
On the text, it is written that they were leaving in a somehow peace in Iran before the revolution, but then after the revolution things got out of hand and they didn't see eye to eye.
A dispute about progression to Muhammad as a caliph of muslims spread crosswise over different parts of the world, which prompted the Battle of Jamal and Battle of Siffin.
The present statistic breakdown between the two groups is hard to evaluate and changes by source, yet a decent estimation is that 85– 90% of the world's Muslims are Sunni[1] and 10– 15% are Shia.