Onkelos son of Kalonikos was the nephew of the Roman emperor — by some accounts Hadrian, by others Titus — and one of the great converts to Judaism in the Talmudic age. When Onkelos embraced the Torah, it was a scandal at the highest level of the empire. The emperor could not have a royal nephew trading eagles and togas for tefillin and a Hebrew name.
A legion was dispatched to bring Onkelos back to Rome. They arrived at his house armed, credentialed, and confident.
Onkelos received them politely. He sat down and began to teach Torah — not as an argument, not as a sermon, but as a man who had been given a secret too beautiful to hide. The soldiers listened. They were supposed to arrest a renegade and return him in chains. Instead, by the time the conversation ended, every one of them had converted.
The emperor sent a second legion, stricter than the first. Onkelos spoke with them as he had with the others. The second legion converted. He sent a third, with orders not to speak with the prisoner at all, to simply take him. As the soldiers marched him out, Onkelos touched the mezuzah on his doorframe. They asked him what it was. He told them: the king of a human kingdom sits inside while his guards stand outside, but the King of the world stands outside while His children sit within, protected by His Name (Avodah Zarah 11a; Gaster, Exempla No. 284).
The third legion converted on the spot.
Rome ran out of soldiers willing to come for Onkelos.
The teaching is hopeful and a little funny. When the Torah is shown rather than argued, it disarms its captors. The emperor could muster armies. He could not muster an argument.