In 718, the Umayyad caliph Umar II finally forbade the levying of extraordinary taxation and slave tributes from non-Arab Muslims, defusing much of the tension. But expensive military reverses in the 720s and 730s had forced caliphal authorities to look for innovative ways to replenish their treasuries. During the caliphate of Hisham from 724, the prohibitions were sidestepped with reinterpretations (e.g. tying the "kharaj" land tax to the land rather than the owner, so that lands that were at any point subject to the "kharaj" remained under "kharaj" even if currently owned by a Muslim).