The Alliance System was created by Otto Von Bismarck, a German statesman, in 1879 when he forged a secret alliance with Austria-Hungary. This alliance was designed to ensure that if anyone attacked either of the two powerful countries, then either Germany or Austria-Hungary could count on one another to come to the other's aid.
This system spread throughout Europe until nearly all the countries in the continent were allied with another in some way. This is what brought about the massive retaliation upon the assassination of Archduke Franz Ferdinand.
The forging of secret treaties and alliances in Europe