Dense Pack is a strategy for basing intercontinental ballistic missiles (ICBMs) for the purpose of maximizing their survivability in case of a surprise nuclear first strike on their silos conducted by a hostile foreign power. The strategy was developed under the Reagan administration as a means of safeguarding America's inventory of MX missiles during the final decade of the Cold War. The U.S. commitments under the Anti-Ballistic Missile (ABM) Treaty prevented the development and staging of adequate ABM installations around its nuclear missile silos. Therefore, it was decided that new and unconventional strategies for protecting these military assets from a sneak-attack had to be developed: "Dense Pack" was one strategy. Other ICBM basing strategies considered during this time were scatterpack, deep basing, rail-mobile, alert ground dispersal, and reverse-inclination basing.
According to the Dense Pack strategy, a series of ten to twelve hardened silos would be grouped closely together in a line. This line of silos would generally run north-to-south, as the primary flight path for Soviet inbound nuclear missiles would be expected to come from the north over the North Pole. The rationale for this thinking went like this: As the first inbound warhead detonates over its target silo, it would throw a large cloud of debris over the entire missile field. Every other warhead targeted on that missile field would have to travel through that debris cloud to reach its target, and it was theorized that the act of traveling through that debris cloud would "trash" the warhead before it could detonate. Every successful explosion over the missile field would throw more debris up into the air, increasing the chances that each successive warhead would be destroyed before it could trigger. Due to the hardened nature of the missile silos, the military believed that the silos could be destroyed only by a direct hit from a nuclear warhead; warhead air bursts were believed to be ineffective to the task of penetrating the armored silos, as were any "near-miss" ground bursts that might occur from an inaccurate ballistic trajectory. The strategy was mentioned in a speech by President Ronald Reagan in 1982.
The proposed Dense Pack initiative met with strong criticism in the media and in the government, and the idea was never implemented. Detractors of the Dense Pack strategy pointed out a number of flaws. First, the advent of multiple independently targetable reentry vehicles, or MIRV, negated the concept due to their ability to conduct a time-on-target barrage. Simply put, a single missile could deliver a volley of three to twelve warheads to the target where they could each detonate at approximately the same time, thus dispensing with the disruptive debris cloud that Dense Pack relies upon for protection. Secondly, there were widespread doubts at the time that the hardened nature of the armored missile silos were as robust as the military claimed, leading to worries that a single warhead could in fact destroy an entire Dense Pack missile field. Finally, Dense Pack was perceived by some to be a provocative, if not overtly hostile measure at a time when nuclear warfare seemed to be a distinct possibility. Ultimately, the U.S. House of Representatives rejected using the Dense Pack strategy by a 245–176 vote.
The U.S. Air Force reconsidered the use of the Dense Pack strategy in 1986, at least in part to find a way to add 50 additional missiles authorized by Congress only if a "safe" basing strategy could be found. There is no evidence that the Dense Pack strategy was ever implemented.