  We present a hydrodynamic theory of incompressible polar active fluids with
quenched disorder. This theory shows that such fluids can overcome the
disruption caused by the quenched disorder and move coherently, in the sense of
having a non-zero mean velocity in the hydrodynamic limit. However, the scaling
behavior of this class of active systems cannot be described by linearized
hydrodynamics in spatial dimensions between 2 and 5. Nonetheless, we obtain the
exact dimension-dependent scaling exponents in these dimensions.
