More people have been killed in the name of a deity than for any other reason. Mostly wars.

Leading writers like Sam Harris, Richard Dawkins and Christopher Hitchens think so. Examples are The Crusades (Christians vs. Muslims), the 30 Years War & the "Troubles" in Northern Ireland (Catholics vs. Protestants), India and Pakistan wars (Hindus vs. Muslims), Israel vs. Egypt & other Arab neighbors (Jews vs. Muslims), the war against ISIS (Christians vs. Muslims). The "War on Terror" is really the "War on Religion" (radical Islam) but governments and newspapers do not like to use the word "religion".

Religion is cause of war

Nah, competion for resources. Follow the money. Religion is just more publicly acceptable than 'we wanted to kill them so that we could take their stuff'.

I think it's different drives at different times. You have those that just wanted to explore in the beginning of civilization and met others and conflict started. Then you have those who have religious differences and believe they are the chosen ones with the "right" God and way of life. Then you have those who want to feel the power of conquest. Then you can have wars over survival or defense from an aggressor. You can have a war to protect others. Then you have the wars for money and economic treasures. Then you have the wars that mix some of the reasons. The U.S. right now is in an economic war with the rest of the world basically, but that can also include having power over others. I think most wars are about resources in one way or another. It seems most modern wars are about resources. Earlier wars were probably because of more various issues. The only way to stop resource wars is probably in trying to create or harness the power to have sustainable and abundant resources. Then we can fight about something else lol. The problem is that most of the people in charge seem to be closer to the narcissistic/sociopathic/psychopathic mind. They seek and excel at those positions because those positions better fulfill their desires and needs.

No..greed and power is, but religion is a great way to manipulate the population into doing the killing for the powerful people who start the wars.

Here's my take on things:

Cause of many. Justification for most.

National boundaries and territorial appropriation have caused many, long before any of the theist religions came to be invented there were wars. It was usually about dominance and conquest. Since the advent of Christianity there have been countless religious wars waged such as The Crusades in the 12/13th centuries, but it is only cause in part. As is usually the case in these sort of arguments, it is much more complicated and usually includes power struggles and politics. These things are never back and white. So yes I concur with your conclusions.
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More like an excuse.

Greed is the cause and religion the excuse.

I don't think religion starts wars. I t is always to do with overtaking territory. Spouting religion is just a convenient ploy to distract from what is really going on. The more land you are in control of, the richer you are.

Yes, the drive to have power over others and economic gains Is religion in my book. And not leadership.

No, only about 8% of wars in history were caused by religion.

Wars are caused by greed, the lust for power, for resources.

Not the cause, but they help to gather the excuse and to gather people around the fight.
The real cause is always power, resources etc.

Religion has not caused wars as evidenced by the fact that Sunni and Shia Muslim religions are the same except for a disagreement over who was supposed to succeed Mohamud, yet they have no problem killing each other with abandon. It would also be a stretch to blame Japan's territorial expansion and Hitler's madness on religion. Wars, I would surmise are caused by different tribes appearing to be "different" from my own.

No, people and politics. WW1, WW2, American War of Independence, American Civil War, 100 Years War, Napoleonic Wars, Punic Wars, and so on...

I'm going to go with greed. Land, money, power, etc.

The irrationality caused by religion causes people to act in destructive ways, including going to war. The fact that they don't believe that they're really going to die encourages aggression. For example, in a first person shooter people are much more aggressive than they are in real life.

Wars are usually regional while religion is also regional. Correlation not causation.

No.

Absolutely

Absolutely, Positively without a doubt if you are a student of History. History requires a lot of reading by different authors or credibility that leads you to other authors and persons of the same era.
I got started on the Life of Gen. George Patton whom I never understood but having seen the movie and having read the Bio's of Eisenhower, Mac Arthur found Georgie was the most interesting and logical on how to win a war.
Being a Veteran and having some understanding of how FU'd the Military can get with its rules and regulations which cost more lives then actual combat will tell you that Patton won WW11 in Europe which if it had not fallen Japan would have never surrendered.
The irony of it all is that both country's are our most closest allies in every way. Patton warned us about Russia, and Mac about Korea an Viet Nam.
I may also need some input to this but Viet Nam is like 90% or more Catholic. I also remember reading that the Tenets of Hitlers SS was taken from the Jesuit Order. If anyone would want I will go back and research my findings which I recollect but do not have the books at present on my mind.

Many of them...
But it is always about power, influence and money...