In 830, following al-Ma'mun's decision to go on campaign against the Byzantines, the caliph designated Ishaq as his deputy over Baghdad, and also gave him control over the Sawad, Hulwan, and the Tigris districts. During the last years of al-Ma'mun's reign, Ishaq enforced the caliph's directives in Baghdad while the latter remained away from the city; in 832, for example, he carried out al-Ma'mun's instructions that the garrison troops should begin reciting the takbir when performing the prayers.[7]