Luther on the importance of the fight at precisely the one position under assault

"Neither is it of any help if someone would say, 'I will gladly confess Christ and His Word in every other article, except that I may keep silence about one or two that my tyrants may not tolerate, such as both species in the Sacrament and the like.' For whoever denies Christ in one article or word has denied the same Christ in that one article who would be denied by [denying] all the articles, since there is only one Christ in all His words, taken all together or singly."

"Auch hilft nicht, daß jemand wollt sagen:  'Ich will in allen Stücken sonst gern Christum und sein Wort bekennen, ohn daß ich müge schweigen eines oder zwei, die meine Tyrannen nicht leiden mögen [(or: die mein Tyrann nicht leiden mag)], als die zwo Gestalt des Sacraments oder desgleichen.'  Denn wer in einem Stück oder Wort Christum verleugnet, der hat ebendenselbigen Christum in dem einigen Stück verleugnet, der in allen Stücken verleugnet würde, sintemal es nur ein Christus ist, in allen seinen Worten sämptlich und sonderlich."

     Martin Luther, Letter 619 to Count Albrecht von Mansfeld, dated 3 June 1523.  WA Bw 3, 81 ff., trans. Dr. Christopher Brown (except that I have re-consulted the WA edition of the original German and re-introduced here the two emphases ("einem" and "ein") missing at that link).  Cf. Pseudo-Luther on the importance of the fight at precisely the one position under assault.