  We consider bosonized $QCD_2$, and prove that after rewritting the theory in
terms of gauge invariant fields, there exists an integrability condition valid
for the quantum theory as well. Furthermore, performing a duality type
transformation we obtain an appropriate action for the description of the
strong coupling limit, which is still integrable. We also prove that the model
displays a complicated set of constraints, restricting the dynamics of part of
the theory, but which are necessary to maintain the positive metric Hilbert
space.
