 In 1979, after a long debate on the topic, President Jimmy Carter selected the "multiple protective shelters" concept for basing the MX.In this system, the 200 MX missiles would be partnered with many thousands of silos, and the missiles would be moved among the silos so the Soviets would not know where they were.In order to attack the MX fleet and do any significant damage, they would have to attack every silo.