People don't sign treaties that prevent them from doing whatever it is they want to do. It follows that the parties didn't want to develop/overcome ABM systems. When one of the parties changed their mind (under Ronald Ray-guns), the treaty ended.
But it turned out to be very difficult and expensive to build an ABM system that can protect much more than an airbase from ballistic missiles. Protecting something like the entire continental USA was infeasible.
People don't sign treaties that prevent them from doing whatever it is they want to do. It follows that the parties didn't want to develop/overcome ABM systems. When one of the parties changed their mind (under Ronald Ray-guns), the treaty ended.
But it turned out to be very difficult and expensive to build an ABM system that can protect much more than an airbase from ballistic missiles. Protecting something like the entire continental USA was infeasible.