Thanks coffee and Hex
this is a good chart which shows you side by side the differences between Sunni and Shia. On comparison of the two you can see that both sects agree on major fundamental points but have differing beliefs on less a number of important issues (in the grad scheme of things). This is where the tension comes from.
I once asked my husband can they not just agree to disagree and be united as believers in Allah? he answered that Islam is not only a religion it is woven into every part of you life, you must rise early to pray in the morning- you cannot have a lie in, you must slaughter you food in the prescribed way, obtain from certain food and drink, it sets rules about the nature of your relationships with the opposite sex, it enters every part of your life in every moment of it. Therefore these difference may be small in the grand scheme of things but because of the way Islam permeates your life they are magnified. I asked him if he was Sunni or Shia, he said I am Muslim. He said that the successor of Mohammed really doesn't matter to him how many thousands of years.
In Kirkuk (my husbands home city) there is a mix of Kurd (which he his), Turks, Sunnis and Shias and also Christians they mainly have their own areas but on the boundaries of these areas where you find a mix of different people you don't really see a huge difference in daily life. It appears they go about their daily life unaffected by the differing beliefs. I believe this to be the case generally in Baghdad too. From my experience the only time there is trouble between people living together in this way is when an extremist from either sect decides blowing themselves/a car up in an area close by dominated by one particular sect. When this happens on the news you see there is a rise in tension between the sects. Then everything slowly dies down and returns to normal until the next time.
Iraq has the potential to be a great country, it has the wealth from oil which could create wonderful infrastructure and services for its people but it can't. I love it there and people think I am insane! The warmth of the people is like nothing I have experienced. Even though my experiences are based mainly in the Kurdish region and Kirkuk even in the Arab areas I have been to I felt welcome and always safe. I just hope the ISIL don't completely tear apart Iraq and that the government can start to work for the good of all the Iraqi people regardless of religion/sect/ethnicity.