The signing of the START II treaty in January 1993 and the Clinton administration's intentions to further cutting the military budget and reducing nuclear forces prompted STRATCOM to bring the conclusions of the STRATCOM’s View briefing into a formal study of alternative force structures. The study, entitled Sun City, examined nine different force structures, six of which were at the 3,500 START II accountable limit, and three that fell "well below" 3,500 weapons. Option 1 was the "preferred" force structure in STRATCOM's View briefed to the Secretary of Defense in November 1992.

The main objective of Sun City was to "capture the effectiveness" of each force structure option in its ability to hold the threat at risk, its planning flexibility, and its affordability. STRATCOM's core concern was to evaluate -- from the warfighter's perspective -- the impact of few, heavily MIRVed platforms (term used loosely to indicate concentration of weapons on a platform) versus many, lighter MIRVed platforms, and the ability to effectively plan the forces. In doing so, STRATCOM relied on the "rules of thumb" developed in the Phoenix Study to calculate the number of weapons required for a given number of installations.

In assessing the various force structure options, STRATCOM assigned a "penalty for capability lost as compared to Option 1." Changes to the mix of the Triad, for example, were assigned penalties for degraded flexibility and capability compared with Option 1. It is little surprise, therefore, that Sun City concluded that the most capable force structure was the most preferable and that it was undesirable to reduce the force level too much. To that end the smaller force structure options (and target sets) were analyzed mainly for "parametric purposes" for the purpose of "realizing the magnitude of the force structure required for smaller target sets." Overall recommendations for the force structure were:

• Flexibility and capability of the Triad are paramount, especially in light of the thinning target base.

• The size of the force must be sufficiently capable against a range of threats.

• The mixture of bombers, ICBMs, and SSBNs must retain flexibility and capability.

• The force must be affordable.

Sun City not only validated the targeting principles of the 1991 Phoenix Study and became the basis for implementing START II, it was also the force structure that STRATCOM would subsequently promote during the Nuclear Posture Review conducted from October 1993 through September 1994.