Mr. Arens is correct that the only certain method of stopping rocketry is to push the launchers out of range. He also might have observed that long after the Germans were out of range of London, they were able to disrupt supplies through the port of Antwerp. "One does not have to be a rocket scientist or nuclear physicist to understand that the shorter the range of the ballistic missile to be intercepted, the more difficult interception becomes." - Moshe Arens Or, the longer. In both cases, it is a matter of time. Right now it is possible to intercept medium range ballistic missiles with some reliability - if one is willing to pay far more to stop each rocket than it costs. The same was true of tactical ballistic missiles 40 years ago. The very short range missile remains a tough target because the time between launch and arrival is quite small, and the ability to acquire, target and destroy it is limited. The ICBM remains a daunting target because it's velocity is so high.
from the article: Intercepting Qassam rockets