  The proposed International Linear Collider (ILC) is well-suited for
discovering physics beyond the Standard Model and for precisely unraveling the
structure of the underlying physics. The physics return can be maximized by the
use of polarized beams. This report shows the paramount role of polarized beams
and summarizes the benefits obtained from polarizing the positron beam, as well
as the electron beam. The physics case for this option is illustrated
explicitly by analyzing reference reactions in different physics scenarios. The
results show that positron polarization, combined with the clean experimental
environment provided by the linear collider, allows to improve strongly the
potential of searches for new particles and the identification of their
dynamics, which opens the road to resolve shortcomings of the Standard Model.
The report also presents an overview of possible designs for polarizing both
beams at the ILC, as well as for measuring their polarization.
