  We review some recent arguments supporting the upgrade of the International
Linear Collider by a polarized positron beam, in addition to the polarized
electron beam. The examples presented here mainly focus on the impact of
positron polarization on items relevant to new physics searches, such as the
identification of novel interactions in fermion-pair production and the
formulation of new CP-sensitive observables. In particular, in addition to the
benefits from positron and electron longitudinal polarizations, the advantages
in this field of having transverse polarization of both beams are emphasized.
