An oft-neglected conflict in Yemen is settling into a significant strategic victory for Iran, with support for a Shia militant group known as the Houthis handing Tehran the ability to threaten a second major international shipping lane and Saudi Arabia.

Oil and gas, as ever in the modern era, fuels the danger posed by rogue actors in the Middle East. Iran already can target freighters in the Strait of Hormuz, the waterway between the Iranian coast and the eastern side of the Arabian Peninsula. A foothold in Yemen, at the southwestern tip of that peninsula, extends the Iranian reach to the region’s other major oil shipping lane — the Bab el-Mandeb Strait, the choke point linking the Suez Canal and the Red Sea to the Arabian Sea and the open ocean.