Circular and Linear ${\rm e^+ e^-}$ Colliders: Another Story of Complementarity

The remarkable synergy and complementarity between the circular ${\rm e^+ e^-}$ and pp colliders has been extensively discussed. In this short document, we investigate the complementarity between the proposed circular and linear ${\rm e^+ e^-}$ colliders at the electroweak and TeV scale. This complementarity could be exploited on a world-wide scale, if both a large circular and a linear infrastructures were available. A possible implementation of such a complementary program is shown.