The battle for Baiji, site of one of Iraq's major oil refineries, is heating up again. Since May, Islamic State fighters have been chipping away at the Iraqi government's control. Now it seems possible that the empty city and the shuttered refinery could fall.

Iraqi Prime Minister Haidar al-Abadi visited the battlefield this week and emphasized the site's strategic importance to retaking Mosul. What he didn't say was that Islamic State's offensive on Baiji is part of its grand strategy to develop domestic sources of revenue that would help make it a functioning state, instead of a would-be state attempting to achieve legitimacy by beheadings and religious fervor.

Oil is crucial to Islamic State's future success. Even in the Middle East, religion and fear alone aren't enough to achieve legitimate statehood. The Sunni militant group will have to deliver a baseline of governance and services to persist over time, as its utopian dream fades into boring reality.