Every April, New York’s proud Scottish-Americans celebrate their heritage with the Tartan Day Parade, processing up Sixth Avenue in a sea of kilts, to the noble blare of the bagpipes. If you are thinking of attending the festivities next year, however, you might want to keep quiet about having read “The Invention of Scotland” (Yale University Press, 304 pages, $30), a punchy new book by the late historian Hugh Trevor-Roper. For as Trevor-Roper points out with ill-concealed glee, tartan and kilt, those universal badges of Scottishness, are about as authentic as Disneyland. Until the 18th century, no one north of the Tweed had ever seen a kilt; nor did the clans, as legend has it, distinguish themselves by the pattern of their tartans, until they were taught to do so by an enterprising clothing manufacturer. The Scottish costume is, Trevor-Roper shows, simply the latest example of an ancient national habit: the forging of tradition.

The word forging, however, can be taken in two senses. There is the fraudulence of the forger of documents, but there is also the honest labor of the forger of steel; and while Trevor-Roper focuses on the first of these meanings, he does not exclude the second. He recognizes that the invention of Scottish history was a creative act, which helped Scotland to emerge as a cohesive and peaceful modern nation. “The creation, and re-creation, of myth requires a continuous capacity for invention,” he writes, “and its formalization can be seen as a ritual adjustment, a formal accommodation of barbarism to civility.” Because Trevor-Roper was a leading historian of Nazi Germany, he is especially appreciative of the benign forms that Scottish mythmaking took: “In Germany, the ancient barbarisms of the race were revived in all their savagery. … Ritualization would have been better.”