“Patterns” is a term infrequently used in our historical writing; many historians associate it with certain more modern sciences. I have chosen it here in order to stress the need for a somewhat more highly elaborated methodology in the study of the matters discussed below. We are so far from adequate understanding of many of these subjects that we cannot be squeamish about borrowing any applicable method from the faster-moving sciences—whether these devices are to be called “matrices,” “models,” or “patterns” will be a matter of taste. I have, for present purposes, chosen the last, for what I should like to do is to suggest a comparative approach to the history of Muscovite-Tatar relations based upon systems, or patterns, of phenomena so arranged that the logic of the arrangment provides information concerning phenomena about which there is no direct evidence.