About nuclear missile silos.
They are meant to be shown to satellites. Silos are intended to be built strong enough to survive non-direct hits by nuclear missiles. To destroy each of these missile silos, you need one nuclear missile. Plus, the US and the Soviets both build empty silos to confuse the other side. The empty silos contain no missile, but nobody knows which one is empty.
In this way, these silos are good sandbags for their owner. Everybody who has a satellite knows where these silos are, but you need to trade your nuclear weapon with these possible empty silos 1 for 1.
Also, to prevent the enemy from just overlooking these silos and hitting other valuable targets (like cities or military bases), the Soviets and the US set the ratio of the real silo to empty one publicly, so that these silos are worth hitting by nuclear missiles.
So, as you can see, one more silo, one less bomb to other targets.