What was Schönberg's merit for twelve-note music?

Arnold Schönberg dissolved the ties to tonality in his "Three pieces for piano" op.11, published in 1908; his "Five pieces for piano", op. 23, 1923 were already written in a purely dodecaphonic system. In the meantime dodecaphonic works had also been composed by the Russian composer Jef Golyscheff (1914) and Josef Matthias Hauer (1919). Hauer insisted on having the right of priority in the development of 12-note music, but this priority quarrel is meaningless, because Schönberg and Hauer had developed something basically different. 

Origin of the name dodecaphony 

Die 3 Wiener Zwölftonschulen