Iraqi forces successfully broke a siege by ISIS militants on the country’s main oil refinery on Saturday, a day after government forces said they had retaken the nearby town of Baiji. The Baiji oil facility accounts for about a quarter of Iraq’s oil production; by retaking it, Iraqi forces would be able to cut key supply lines for ISIS. Also on Saturday, top U.S. military officer General Martin Dempsey arrived in Iraq on an unannounced visit, his first since the U.S. began a campaign of airstrikes against ISIS.