<P> However, Italian public opinion remained unenthusiastic about their country's alignment with Austria - Hungary, a past enemy of Italian unification, and whose Italian populated districts in the Trentino and Istria were seen as occupied territories by Italian irredentists . In the years before World War I, many distinguished military analysts predicted that Italy would attack its supposed ally in the event of a large scale conflict . Italy's adherence to the Triple Alliance was doubted and from 1903 plans for a possible war against Rome were again maintained by the Austrian general staff . Mutual suspicions led to reinforcement of the frontier and speculation in the press about a war between the two countries into the first decade of the twentieth century . As late as 1911 Count Franz Conrad von Hötzendorf, chief of the Austrian general staff, was advocating a military preemptive strike against Austria's supposed Italian ally . This prediction was strengthened by Italy's invasion and annexation of Libya, bringing it into conflict with the German - backed Ottoman Empire . </P> <P> King Carol I of Romania was of German ancestry . That, coupled with his wish to turn Romania into a centre of stability in South - Eastern Europe (as well as his fear of Russian expansion and their competing claims on Bessarabia), led to Romania secretly joining the Triple Alliance on 18 October 1883 . Only the King and a handful of senior Romanian politicians knew about it . Romania and Austria - Hungary pledged to help each other in the event of a Russian, Serbian, or Bulgarian attack . There were, however, several disputes between the two countries, the most notable being the policy of Magyarization of Transylvania's Romanian population . Romania did eventually manage to achieve the status of Regional Power in the aftermath of the Balkan Wars and the 1913 Treaty of Bucharest, but less than a year later, World War I started and Romania, after a period of neutrality, in which both the Central Powers and the Allies tried persuading Romania to join their respective sides, eventually joined the Allies in 1916, after being promised Romanian - inhabited Austro - Hungarian lands . Romania's official reason for not siding with the Triple Alliance when the war started was the same as Italy's: the Triple Alliance was a defensive alliance, but Germany and Austria - Hungary had taken the offensive . </P>

Who was in each alliance both before and after the war started