A force of 3,500 US sailors and Marines arrived in the Middle East aboard the USS Tripoli — as Tehran warned that American forces will be killed if President Trump orders a ground invasion of Iran. The flagship for the Tripoli Amphibious Ready Group and 31st Marine Expeditionary Unit arrived over the weekend with troops in tow, US Central Command said Saturday. Along with the troops, the amphibious warship brought transport and strike fighter aircraft, as well as assault and tactical assets,