SINCE the days of John Foxe, ecclesiastical historians of the 1520s have concentrated on the Odysseys and Passions of the earliest English Protestants. Their Catholic opponents, with the notable exceptions of John Fisher and Thomas More, have been largely ignored. The object of this essay is to redress the balance by examining the English commitment to orthodoxy in the 1520s, a commitment made primarily by the secular and ecclesiastical authorities, but seconded enthusiastically by the academic community. It aims not to rewrite the entire ecclesiastical history of the decade, but merely to draw attention to an important though neglected element in the story. Nevertheless, it hopes to be a contribution to the reassessment of the English Reformation that has been carried out in much recent research. The essay is primarily an investigation of polemics, rather than of politics or of popular religion. Beginning with Henry VIII's decision early in 1521 to take up the pen personally against Luther, it draws out the connection of this with the promulgation in England of Exsurge Domine, the Papal condemnation of Luther, and suggests a solution to the vexed question of the ‘real’ authorship of Henry's Assertio Septem Sacramentorum. It investigates the continuation of this polemical assault on Luther by English scholars; and examines its international dimension, gathering evidence of the patronage and cooperation extended to Luther's continental opponents by the English authorities. In conclusion it proposes that the strongly orthodox commitment of the English authorities in the 1520s ebbed away only as the pressing needs of the ‘King's Great Matter’ occasioned competing, and ultimately conflicting, intellectual priorities.