19 14 years, World War I broke out, Germany and Austria-Hungary were allies, and Britain, France and Russia were allies. However, Italy, one of triple alliance, joined the Allies in 19 15. Why?

First of all, this is determined by Italy's weak and foreign expansion policy. 187 1 year, risorgimento has been divided for a long time, which provides favorable conditions for the development of capitalism. However, the unification was completed from top to bottom, retaining a large number of feudal remnants, which seriously hindered the further development of Italy's economy and caused Italy's backwardness, mainly in three aspects: First, agriculture was backward, grain output was extremely low, and one third of the grain was imported every year. Second, heavy industry is underdeveloped and lags far behind other imperialist countries. Third, people's lives are extremely difficult, and a large number of poor people have fled abroad to make a living. Therefore, Italy is called "poor imperialism". Like other imperialist countries, Italy is actively expanding its foreign colonies. However, due to its own weakness, its expansion attempt can only be realized by the hegemony of big countries, which is doomed to the vacillation of Italy's foreign policy, and whoever is beneficial to its hegemonic expansion will rely on it.

Secondly, this is also determined by Italy's national interests. Italy, Britain, France and Russia have many common interests, which are embodied as follows: Italy can't afford to offend Britain, because its long coastline can't stand the attack of the powerful British navy, so it said from the beginning that it would not participate in any action against Britain. "Poor imperialist" Italy is financially dependent on "usurious imperialist" France. Especially after 1887 and 1895 failed twice, Ethiopia was forced to unconditionally recognize its independence and compensate 1000 Wan Li, which caused serious financial and economic difficulties in Italy. At this time, France seized the opportunity on the condition of loan. In order to expand smoothly in Africa, Italy also reached an agreement with Russia. The two sides signed a contract to jointly resist the expansion of Austria-Hungary in the Balkans, and intended to adopt a "goodwill attitude" towards Russia's expansion in the Black Sea Strait. Russia understands its intention to expand in North Africa. It can be seen from the above facts that before the outbreak of World War I, Italy had actually split from the triple alliance and stood on the side of the allies because of its interests.

Third, after the outbreak of World War I, the Allies all met the requirements of Italian territory. After the outbreak of World War I, Italy declared "neutrality" on the pretext that Austria-Hungary declared war on Serbia without consulting Italy, in an attempt to bargain with the warring parties on the condition of participating in the war in order to obtain more benefits. Later, the Allies met all the requirements of Italy, especially the land promised to Italy was twice that promised by Germany. In addition, Britain also lent Italy a lot of debts, so in May 19 15, Italy declared war on Austria-Hungary and formally joined the Allies.