- Karen Armstrong
plunder and a common activity that would preserve the unity
of the ummah. For centuries the Arabs had tried to raid the
richer settled lands beyond the peninsula; the difference was
that this time they had encountered a power vacuum. Persia
and Byzantium had both been engaged for decades in a long
and debilitating series of wars with one another. Both were
exhausted. In Persia, there was factional strife, and flooding
had destroyed the country's agriculture. Most of the Sassa-
nian troops were of Arab origin and went over to the in-
vaders during the campaign. In the Syrian and North African
provinces of Byzantium, the local population had been alien-
ated by the religious intolerance of the Greek Orthodox es-
tablishment, and were not disposed to come to their aid when
the Arabs attacked, though Muslims could make no headway
in the Byzantine heartlands of Anatolia.
Later, when the Muslims had established their great em-
pire, Islamic law would give a religious interpretation of this
conquest, dividing the world into the Dar al-Islam (the House
of Islam), which was in perpetual conflict with the Dar al-
Harb (the House of War). But in practice the Muslims ac-
cepted that they had reached the limits of their expansion by
this date, and coexisted amicably with the non-Muslim world.
The Quran does not sanctify warfare. It develops the notion
of a just war of self-defence to protect decent values, but con-
demns killing and aggression.19 Furthermore, once the Arabs
had left the peninsula, they found that nearly everybody be-
longed to the ahl al-kitab, the People of the Book, who had
received authentic scriptures from God. They were not,
therefore, forced to convert to Islam; indeed, until the middle
of the eighth century, conversion was not encouraged. The
Muslims assumed that Islam was a religion for the descen-
dants of Ismail, as Judaism was the faith of the sons of Isaac.
Arab tribesmen had always extended protection to weaker
clients (mawali). Once the Jews, Christians and Zoroastrians