By 696 there was a new governor of Khurasan, Umayya, appointed by the caliph Abd al-Malik. He was a member of the ruling Umayyad family, easygoing, generous, peace-loving, and, his enemies alleged, pompous and effeminate. He was to have a hard struggle keeping the unruly Arabs of Khurasan in order. The most effective way of doing this was to lead them in campaign across the Oxus, today’s Amu Darya, to fill their minds with thoughts of Holy War and booty, rather than tribal feuding and vengeance.

Preparations were made for a major campaign against Bukhara. Umayya spent a vast amount of money on horses and weapons. For impoverished and discontented Arabs, a raid across the river with the prospect of serious booty was a very attractive proposition.

In the event, Umayya does not seem to have commanded the respect and confidence of his troops, and the expedition was a fiasco. After he and his men had crossed the bridge of boats over the Oxus at Amul, his second-in-command refused to follow him any further, crossing back over the river with some of his men, burning the boats, and heading back to take over Merv and establish himself as governor. Appeals to Muslim solidarity failed to move him, and he shrugged off concerns about the fate of the Muslim forces under Umayya’s command, now cut off beyond the river, saying that they had numbers, weapons, and courage, and that they could go as far as China if they wished.

From Hugh Kennedy’s The Great Arab Conquests: How the Spread of Islam Changed the World We Live In, London: Weidenfeld & Nicholson, 2007, pp. 241-242.