At first, even Heisenberg had heated disputes with Bohr that his matrix mechanics was not compatible with the Schrödinger's wave mechanics. And Bohr was at first opposed to Heisenberg's uncertainty principle. But by the Fifth Solvay Conference held in October 1927 Heisenberg and Born concluded that the revolution was over and nothing further was needed. It was at that last stage that Einstein's skepticism turned to dismay. He believed that much had been accomplished, but the reasons for the mechanics still needed to be understood.