About 40,000 U.S. personnel are spread throughout the region, giving Iran a chance to strike back at American military forces.

More than two dozen U.S. Air Force KC-135R and KC-46A tankers took off from bases across the U.S. and headed east over the Atlantic, The War Zone reported earlier. The U.S. Navy's aircraft carrier USS Nimitz has also appeared to be heading toward the Middle East from Asia.