Titan was originally planned for a 1 X 10 (one control center with 10 launchers) "soft" site. In mid-1958 it was decided that the American Bosh Arma all-inertial guidance system designed for Titan would, because production was insufficient, be assigned to Atlas and the Titan would switch to radio-inertial guidance. The decision was made to deploy Titan squadrons in a "hardened" 3 X 3 (three sites with one control center and three silos each) to reduce the number of guidance systems required. (Radio-inertial guided Atlas D squadrons were similarly sited).