Why did the European alliance systems develop before World War I?

In the late 1800's, there was a lot of distrust between the major powers of Europe.  A lot of the tension was caused because of competition for colonies in Africa.  Nations formed alliances as a result of this distrust and to protect themselves from aggression.  Germany, Austria-Hungary and Italy formed the Triple Alliance (1882) because of their dislike of France and Russia.  Germany, in particular, was surrounded on both sides by these powers and felt the need to expand its military power through the alliance.  France and Russia responded by forming an alliance twelve years later.  These alliances also were formed to forge economic ties through trade agreements but were mostly aimed at military protection.   By 1907, Britain, France, and Russia formed a formal alliance that would endure until the beginning of World War I.  Germany and Austria-Hungary were committed to their Alliance for the duration of World War I, but Italy would join the side of Britain and France.  So while the Alliances were initially created to forge a sense of security, they actually led to a very large conflict in Europe.