  We extend the Keldysh formulation to quantum spin systems and derive exact
equations of motion. This allows us to explore the dynamics of single spins and
of ferromagnets when these are inserted between superconducting leads. Several
new effects are reported. Chief amongst these are nutations of single S=1/2
spins in Josephson junctions. These nutations are triggered by the
superconducting pairing correlations in the leads. Similarly, we find that on
rather universal grounds, magnets display unconventional spin wave dynamics
when placed in Josephson junctions. These lead to modifications in the
tunneling current.
