This 1983 work, his first on topics of medieval Jewish history, shows Dr Cohen's acumen. He takes on the intricate topic of mapping the overlap of Catholic mendicant preaching (the Dominicans and Franciscans exclusively; this led me to ponder if other Orders such as Augustinians, Carmelites, Trinitarians or Mercedarians--the latter two pledged to redeem captives from prison and Muslim slavery, had anything to add to the polemics) and Jewish defenses against concerted Church attacks.
Cohen explains that Augustine led the way for earlier medieval clerics to allow limited tolerance of their Jewish brethren, since the final days and Christ's return can't happen until after their mass conversion. But later factors, as Jews persisted in their adherence to rabbinical, post-"biblical" laws and observances even as the Christian messiah superseded the Mosaic Law, and invalidated the Talmudic rules by which subsequent Jews refused to give up as they opposed the 'true Faith," led to increasing calls from the friar-preachers to call for their forced or coerced baptisms, the exile, or eventually the eradication of those who held out against the calls to unify the Church, especially following the 1215 Lateran Council. Plus the fears that heresy and persuasion from "Judaizers" could sway Christians from their "new covenant" back to the discredited "old" ways of the minority faith.
By the way, the Inquisition in the 13c didn't have the cohesion it has been credited with by its fierce legions of detractors in later centuries, so Cohen doesn't attend much to its impact in its nascent decades. He reminds us that only those who had lapsed from their turn to Christian fidelity and had returned to their born-Judaism were technically under the thumb of this penal power imposition. However, certainly instances abounded where the legalities must have been ignored or overridden?
Also, relying on, unsurprisingly, erudite rather than popular sources, this dissension feels like it's happening in a vacuum apart from the real-life encounters between Jews and Christians. Opening up these exchanges, say in commerce, would've enlivened the tone and expanded the range of Cohen's mission. Since the Order of Friars Minor early on, after St Francis' visit to the Sultan in Damietta, were granted custody of the Holy Land's shrines, how might this privilege have figured in as to how their brothers tapped into the Jewish vs Islamic dynamic in Zion? Did this reverberate at all into European society, given repeated Crusades, pilgrimages, and devotions active in that realm?
Anyhow, this study is the first book-length analysis of this long-overdue theme. I'd have liked in-depth excerpts from actual preachers such as the Franciscan Berthold of Regensburg, whom Cohen attributes with immense success among the laity. Why cite rather sparingly his homiletic appeals? Cohen focuses on where the information is, sure, but there's far less attention to the "street value" that the content delivered by the mendicants to their urban flocks had in everyday, functional acts.
And to such as these largely unlettered folks swayed from the pulpit, Cohen emphasizes how friars' messages that the contemporary Jews no longer merited papal protection, state security, or Catholic charity--if they dug in against bowing to the Church's heavy hand--may have increased stubborn prejudice against "the Jews" in later centuries as the Black Death hit and opposition to "Rome rule" widened. These aftermaths are beyond the scope of his study, but I bet historians following in his footsteps have expanded their investigations based on the ground cleared by Cohen's scholarship.