The Brockett-Wegner diagonalizing flow Ḣt = [ Ht, [Ht, A] ] is studied. Global existence and uniqueness of solutions of this evolution equation is proved on the space B[H ] of bounded operators on a complex Hilbert space H . Local existence is proved for certain unbounded initial operators H0. Furthermore, if H0, A are Hilbert-Schmidt operators, it is demonstrated that Ht strongly converges to ...