US military action has so far failed to halt attacks by Iran-backed groups on Washington's forces in the Middle East and shipping in the Red Sea, with the threats persisting despite recent heavy air strikes.
The attacks by militants -- which the armed groups that claim them say are driven by the Israel-Hamas war -- have been launched from or hit four different countries, posing a multi-front challenge for the United States, which aims to curb the unrest while avoiding direct conflict with Iran.
