Answer:
Countries formed alliances to protect their colonial empires.
Step-by-step explanation:
In the 19th century, major European powers sought to maintain a balance of power in Europe, which resulted in the existence of complex networks of political and military alliances across the continent by 1900. This began in 1815 with the creation of the Holy Alliance between Prussia, Russia and Austria. Then, in October 1873, German Chancellor Otto von Bismarck arranged for the League of Three Emperors (German: Dreikaiserbund) between the emperors of Austria-Hungary, Russia and Germany.
In 1882, this alliance was expanded by Italy to become the Triple Alliance. Two years later, a Franco-Russian alliance was signed to oppose the Triple Alliance.
In 1904, the United Kingdom signed a series of agreements with France, and in 1907 the United Kingdom and Russia signed the Anglo-Russian Convention. Thus Britain entered into an alliance with France and Russia which became known as the Entente.