Austria-hungary wanted to expand its empire into the country of serbia. gavrilo princip, a member of a serbian terrorist organization, assassinated archduke of austria-hungary (heir to the throne). this set off a series of events which caused austria-hungary and germany to declare war on serbia. this also brought in serbia’s friend and the other members of the triple entente. did not join its fellow triple alliance members but instead switched sides and joined the triple entente and serbia to form a new alliance called the allied powers (aka the allies). germany, austria-hungary, and the ottoman empire (turkey) formed a new alliance called the central powers.