Was ancient Judaism a missionary religion? Well, it depends on what you mean by “missionary.”
In one sense—say, in contrast to Christianity—Judaism, with one exception of short duration, never was. From earliest times Christianity saw the propagation of its faith as one of its central tenets. Early Christians taught that paganism was empty and worthless and that only through Christianity could humanity be saved. When the imperial government became Christian in the fourth century C.E., the emperors of Rome embarked on a policy to eradicate paganism. And, indeed, paganism was eradicated. This policy was inherited and implemented by the various European states that succeeded the Roman Empire in the West. Missionaries were sent to the darkest corners of the world to illuminate them with the light of Christ.