carry many warheads (up to 8 in existing U.S. missiles, limited by New START, though Trident II is capable of carrying up to 12) and deliver them to separate targets. If it is assumed that each side has 100 missiles, with 5 warheads each, and further that each side has a 95 percent chance of neutralizing the opponent's missiles in their silos by firing 2 warheads at each silo, then the attacking side can reduce the enemy ICBM force from 100 missiles to about 5 by firing 40 missiles with 200 warheads, and keeping the rest of 60 missiles in reserve. As such, this type of weapon was intended to be banned under the START II agreement, however the START II agreement was never activated, and neither Russia nor the USA has adhered to the agreement. Destabilizing role of missile defense Any defense system against nuclear missiles such as SDI will be more effective against limited numbers of missiles launched. At very small numbers of targets, each defensive asset will be able to take multiple shots at each warhead, and a high kill ratio could be achieved easily. As the number of targets increases, the defensive network becomes "saturated" as each asset must target and destroy more and more warheads in the same window of time. Eventually the system will reach a maximum number of targets destroyed and after this point all additional warheads will penetrate the defenses. This leads to several destabilizing effects. First, a state that is not building similar defenses may be encouraged to attack before the system is in place, essentially starting the war while there is no clear advantage instead of waiting until they will be at a distinct disadvantage after the defenses are completed. Second, one of the easiest ways to counter any proposed defenses is to simply build more warheads and missiles, reaching that saturation point sooner and hitting targets through a strategy of attrition. Third, and most importantly, since defenses are more effective against small numbers of warheads, a nation with a defense system is actually encouraged to engage in a counterforce first strike. The smaller retaliatory strike is then more easily destroyed by the defense system than a full attack would be. This undermines the doctrine of MAD by discrediting a nation's ability to punish any aggressor with a lethal retaliatory second strike. See also Dead Hand, a Soviet nuclear retaliation