  We study both of the scattering and Cauchy problems for the semilinear wave
equation with null quadratic form on the Schwarzschild background. Prescribing
the scattering data that are given by the short pulse data on the future null
infinity and are trivial on the future event horizon, we construct a class of
globally smooth solutions backwards up to any finite time and show that the
wave travels in such a way that almost all of the (large) energy is focusing in
an outgoing null strip, while little radiates out of this strip. In reverse,
considering a class of Cauchy data with large energy norms, there exists a
unique and global solution in the future development. And most of the wave
packet is confined in an incoming null strip and reflected to the future event
horizon, whereas little is transmitted to the future null infinity.
