A S far as I have been able to discover, the diplomatic relations be-
tween the 'Abbāsid and Carolingian houses have never been
treated in English within the compass of a single essay. Certain as-
pects, as for instance the so-called Frankish Protectorate, have re-
ceived considerable attention, but their treatment has always been
in isolation from the political situation prevailing in Christendom or
Islām, and but scant attention has been paid to the affairs of Spain.
In addition, the significance of the gifts of the Caliphs to the Frank-
ish kings and the diplomatic etiquette observed have been com-
pletely ignored.

In my own work in the political theory of Oriental Despotism, I
was confronted with the place of the robe of honour in the ceremonial
of commendation in the East, and the idea of applying the theory to
the interpretation of Charles the Great's relations with Hārūnu'l-
Rashīd appeared to be a fruitful one. In 1925 my attention was
drawn to the relics of the pallium of Saint Cuthbert and the kalima
woven into the purple robe. In a description of the relics, published
in Archaeologia Aeliana, I gave a summary of the theory as a possible
solution of the presence of a Muslim robe on the body of a Christian
saint, but, within the limits prescribed, adequate treatment was im-
possible.

In the following essay, this theory has been developed and the re-
sults compared with the conclusions of Barthold, Vasiliev, and others,
and I submit that in the light of the Umayyad and 'Abbāsid feud
there is nothing inherently improbable either in the negotiations or
in the form they took, particularly if the suggestion to Pippin came
either from discontented Spanish amīrs or from Alexandria or from
both. The fundamental condition to be borne in mind is that the
approach made by Pippin, and later by Charles, to the Khalīfah
placed them both in the status of petitioners, while the political
framework underlying the negotiations was primarily Muslim.
Hence, it follows that the whole chapter lies within the realm of
Muslim rather than Christian history. In that light the grant of a
'protectorate' or wilāyat over the Holy Places is admissible; but it is

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