Complex sentence: It was founded in 1906 as a merger of fifteen smaller unions, as a result of the inability of the previous unions to control the radical elements of the workers movement in the railworkers' strike of 1903.
Split into simpler sentences: It was founded in 1906 as a merger of fifteen smaller union. The reason for the foundation was the inability of the previous unions to control the radical elements of the workers movement in the railworkers' strike of 1903.