What caused world war one to brainliest !

Heyo,  

World war one started because of  the assassination of Archduke Franz Ferdinand of Austria-Hungary. ... When Russia began to mobilize due to its alliance with Serbia, Germany declared war on Russia.

The simplest answer is that the immediate cause was the assassination of Franz Ferdinand, the archduke of Austria-Hungary. His death at the hands of Gavrilo Princip – a Serbian nationalist with ties to the secretive military group known as the Black Hand – propelled the major European military powers towards war.

Do you understand?

ill take that ty XD

in 1897, pershing became a tactical officer at west point, and that's where he was given the nickname "black jack." pershing's first name is "john," for which "jack" is a nickname, and he was a white man who commanded black troops. hence "black jack".