It is the greatest concentration of American airpower in the Middle East since the 2003 invasion of Iraq — assembled to prepare for possible military strikes on Iran, even as diplomacy continues. Two carrier strike groups are converging on the region. Fighter squadrons are flowing into bases from Jordan to Qatar, bridged across the Atlantic by aerial refueling. Submarines and destroyers armed with Tomahawk cruise missiles patrol nearby waters. Patriot and THAAD batteries have been rushed