World war I & II. Atheists, Christians or Muslims? Who is responsible? And who will be responsible for the III world war?

World War One: One person who strongly supported Serbian power sent men to kill Archduke Franz Ferdinand of Austria. They all failed to kill him with grenades while he passed through a large crowd but one of these men, a Bosnian student named Gavrilo Princip, shot him and his pregnant wife (Sophie) with a pistol.

Austria-Hungary blamed Serbia for the assassination. Germany, which supported Austria-Hungary, said that they should make a list of things that Serbia should do as punishment for killing the Archduke. Austria-Hungary was very strict with these rules, possibly because they wanted an excuse to start the war. Though Serbia agreed to most of ten of the things on the list, they could not agree to them all. Austria-Hungary then declared war on Serbia. This quickly led to a full-scale war. Both country's allies became involved in the war.

World War Two: The start of the war is usually said to be the Invasion of Poland on 1 September 1939, but some sources count the Japanese invasion of China on 7 July 1937, as the start of the war.

So it was neither the atheists nor the Christians nor the Muslims - and there will not be a WW3.

None of them. WW I was triggered by a royal assassination at the hands of anarchists, and WW II was the result of 4 nations (Germany, Japan, Italy and Turkey), attempting to dominate the globe. As for your hypothetical WW III, there is neither indication that it will occur, nor is there any way to predict the specific cause. Your attempt at trying to draw parallels between religious philosophy and geo-political strife is weak.

I guess it was Bronies

SATAN.