Cambridge Ancient Hi.. - Index of

mecca, muhammad and the rise of islam 699
others and in its proper place’. 110 In this way a small force could soon swell
to thousands as warriors joined its ranks in expectation of adventure,
fighting and plunder.
The situation was made more difficult by the fact that confronting the
Arabs on this scale posed entirely new military problems. Both powers
were accustomed to dealing with Arabs as bands of raiders and had
planned their frontier defences accordingly. Watchtowers and forts, many
of them abandoned for centuries in any case, were inadequate to deter the
forces that now swept past them, and whereas the old Roman system had
anticipated incursions by single uncoordinated bands, it was now confronted
by penetration at many points simultaneously. It was probably also
difficult to determine exactly where the enemy was at any given time, for
when battle was not imminent an Arab army tended to fragment into bands
of warriors roaming the countryside.
Finally, and as the above example shows, Arab strategy was often highly
reactive and thus difficult to counter or predict. Incursions into Iraq, for
example, seem to have begun when the tribe of Rabī�a, of the Banū
Shaybān, was obliged by drought in Arabia to migrate to Iraqi territory,
where the Sasanian authorities permitted them to graze their herds on
promise of good behaviour. But the presence of these tribal elements
eventually led to friction, which the Rabī�a quite naturally interpreted as
unwarranted reneging on an agreed arrangement. When they called on
their kinsmen elsewhere for support, the crisis quickly escalated into fullscale
conflict between Arab and Persian forces. 111
It is difficult to guess whether either of the great powers would have
been able to stem the military momentum that was building in Arabia, even
had they correctly gauged the threat it posed. With Kinda, the Ghassānids
and the Lakhmids all in a state of either collapse or disarray, the growing
strategic power of Islam was able to develop in what otherwise amounted
to a political void; the real source of the danger confronting the empires
was effectively beyond their reach from the beginning. Byzantium and
Persia could fight armies that violated their frontiers, but could not stop the
process that was generating these armies in the first place. Initial victories
over the Arabs at Mu�ta in Syria in 632 and the battle of the Bridge in Iraq
in 634 thus proved no deterrent, as in earlier times would have been the
case. 112
What overwhelmed the Byzantines and Sasanians was thus the ability of
the message and charismatic personality of Muh · ammad to mobilize the
tribal might of Arabia at a level of unity never experienced among the
Arabs either before or since. Unprepared for defence on the scale required
110 Ibn �Asākir i.446. 111 Ibn A�tham al-Kūfī, Kitāb al-futūh· i.88–9.
112 Donner (1981) 105–11, 190–202; Kaegi (1992) 71–4, 79–83.
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