King Sisebut ascended the Visigothic throne in 614 CE and began an earnest persecution of Jews in his kingdom. He decreed that every Jewish man who did not have his children and servants baptised within the year would receive 100 lashes, be deprived of all his property, and be banished from the kingdom. 614 CE was also the year Jerusalem fell out of Catholic Byzantine hands and under Jewish autonomy for the first time since Hellenization. This enraged Catholic clergymen across the continent, and in Visigothic Spain it started a proto Inquisition complete with the introduction of the rack as torture device.
Over the next six years, Sisebut and his Catholic bishops compelled some 90,000 Jews to be baptised. Border guards patrolled the edges of the kingdom to prevent Jewish escape, although a few were amenable to bribery. The Archbishop of Seville Isidore protested the use of violence and force to compel Jewish conversion, passing a canon law at the fourth Synod of Toledo to that effect, but it was weak and never enforced. With the death of Sisebut’s son and successor, the plight of the Jews finally relaxed some. Some baptised Jews continued worshiping in secret.
When the Visigoths had converted to Catholicism, it had redistributed power from the nobles to the church. Under Arianism, Jesus was considered a created being – first among equals. Likewise the king was considered the first among the nobles, slightly elevated but not so different. Not a god. Catholicism lent itself to monarchy over democracy. The price of entry was giving the bishops power, and one way they wanted to express that power was antisemitism. Another was way taking it from the nobles.
In the Synod of 633 the bishops gave themselves the power to choose the king from among the members of the royal family, a right previously held by the nobility. The clergymen also declared that every Jew must be baptised. Four years later the king would issue an unenforced decree kicking out all Jews, before being distracted by a period of war and many successors. King Chindeswinth took the throne in 641 CE and fought back against a clergy grown too powerful, giving Jews a nine year reprieve until his death.
His son King Reckeswinth seems not to have had his resolve. Jewish persecution laws were reinstated and even baptised Jews were horribly mistreated. A letter to the Eighth Synod of Toledo from converted Jews begs for their persecution to end, swears they have forsaken their Jewish roots, and promises to burn or stone to death any of their members who “relapse” into Judaism. The conditions that must have existed to compel them to write that entreaty are difficult to imagine.