Editing Safeguard Program (section)

===Nike Zeus===
{{main|LIM-49 Nike Zeus}}

An anti-ICBM defensive ABM system was first considered by the US Army in 1955 under the name Nike II. This was essentially an upgraded version of their [[MIM-14 Nike Hercules|Nike B]] [[surface-to-air missile]] (SAM) along with dramatically improved [[radar]]s and [[computer]]s able to detect the incoming [[reentry vehicle]]s (RVs) and develop tracking information while still leaving enough time for the interceptor missile to climb to its altitude. Zeus had limited ''traffic handling'' capabilities, designed to deal with a small number of attacking missiles arriving over a period of as long as an hour. It was calculated that an attack of only four missiles arriving within one minute would allow one of the warheads to pass by while the system was busy attacking others, making it relatively easy to attack the Zeus base. However, in an era when ICBMs cost about the same as a [[strategic bomber]], such an attack would cost an enormous amount.{{citation needed|date=September 2015}}

Through the late 1950s a new generation of much lighter [[thermonuclear bomb]]s cut warhead weight from {{convert|3000|kg}} in the case of the original Soviet [[R-7 Semyorka]] ICBM to perhaps {{convert|1000|kg}}, and further reductions were known to be possible - the US's [[W47]] of the [[UGM-27 Polaris]] weighed only {{convert|330|kg}}. This meant that much smaller rockets could carry these new warheads to the same range, greatly reducing the cost of the missile, making them far cheaper than bombers or any other delivery system. When [[Nikita Khrushchev]] angrily boasted that the Soviet Union was producing new missiles "like sausages", the US responded by building more ICBMs of their own, rather than attempting to defend against them with Zeus. Adding to the problems, as the warhead weight dropped, existing missiles had leftover [[throw weight]] that could be used for various [[Radar jamming and deception#Mechanical jamming|radar decoys]], which Zeus proved unable to distinguish from the actual RV. The Army calculated that as many as twenty Zeus' would have to be fired to ensure a single incoming missile was destroyed.{{citation needed|date=September 2015}}