US-Soviet negotiations on mutual troop reductions and the strategic nuclear arsenal caused severe tensions. Luns convinced American leaders that it undermined the credibility in Western Europe of their nuclear strategy by neglecting European fears of a change of strategy which would leave Europe unprotected in case of a Soviet nuclear attack. The modernisation of the tactical nuclear forces by the introduction of the neutron bomb and cruise missiles caused deep divisions. In the end, Luns succeeded in keeping NATO together in the so-called Double-Track Decision of December 1979. The deployment of these new weapon systems was linked to success in American-Soviet arms reduction talks.