Nothing happened in 1915.
None of their expectations were fulfilled in 1914, but WWI was a major event. . . . so they then claimed WWI as proof of the last days begining. One problem is, and there are many, is that the last days were taught to have begun in 1799, and 1914 was supposed to spell the end of the last days, not the start. . . . . anyway fast forward almost a hundred years and the society has fixed all their past errors by rewriting their history and what they actually believed and expected to happen for 1914, in order to make themselves look like some divinely appointed prophet of God.
They can tell the JWs what they want about their history, and if any JWs do research into the Society and become aware of their lies and deceit, they risk being DF'd for a mental disease.