As if the more far-seeing Jews had anticipated the approach of the gloomiest era of Spanish Judaism, they provided their co-religionists for the coming struggle with casque and buckler, so that the inexorable foe might not surprise them unarmed. A Spanish Jew, contemporary with Moses de Tordesillas, compiled a polemical work, more exhaustive than its predecessor, defending Judaism and attacking Christianity. Shem-Tob ben Isaac Shaprut of Tudela had at an early age been forced into the position of a defender of his brethren against proselytizing attempts. Cardinal Don Pedro de Luna, who later on, as Pope Benedict XIII, brought so much confusion into the church and evil on the Jews, was possessed of a perfect mania for conversion and religious controversy. At Pampeluna he summoned Shem-Tob ben Shaprut to a debate on original sin and salvation, and the latter was compelled to sustain his part in the presence of bishops and learned prelates. The war between England and Castile, the scene of which was Navarre, obliged Shem-Tob ben Shaprut, with many other Jews, to quit the country (1378) and settle in the neighboring town of Tarazona, in Aragon. Observing here that Jews of the stamp of John de Valladolid were extremely zealous in the promotion of religious discussions, the conversion of weaklings, and the maligning of Jewish literature, he published (1380) a comprehensive work ("Eben Bochan"), unmasking the speciousness of the arguments deduced by Christian controversialists from the Bible and the Talmud. The work is written in the form of a discussion between a believer in the unity of God and a Trinitarian. To enable the Jews to use weapons out of the Christian armory, Shem-Tob ben Shaprut translated into Hebrew extracts from the four Gospels, with incisive commentaries. Subsequently the anti-Jewish work of the apostate Abner-Alfonso fell into his hands, and he refuted it, argument by argument.