Militarily, the war has been in a virtual stalemate for more than two years. In the process, the country has been geographically fractured, reversing the widely heralded unification of Marxist South Yemen and pro-Western North Yemen after the Cold War ended, almost three decades ago. In the chaos, both isis and Al Qaeda of the Arabian Peninsula have gained followers and a foothold. The United States doesn’t want jihadists to exploit another failed state. During more tranquil times, in 2000, Al Qaeda suicide bombers struck the U.S.S. Cole during a refuelling stop in Aden, a port city in southern Yemen. Seventeen U.S. sailors were killed.

The United States has also been sucked into the war by arming, aiding, and advising its Gulf allies. Under both the Obama and Trump Administrations, Washington has provided intelligence, aircraft, bombs, and other armaments to Saudi Arabia and the United Arab Emirates. U.S. military planes have aerially refuelled Saudi bombers—less than twenty per cent, Mattis said. Critics, nonetheless, say the American refuelling makes the U.S. complicit in Saudi air strikes that kill civilians.

The Trump Administration now faces growing pressure from Congress, particularly from Republicans, to curtail arms sales to the kingdom until the war ends. This week, five prominent senators, led by Marco Rubio, also pressed the White House to terminate talks with the kingdom on civil nuclear coöperation.