escorts to accompany ROC convoys up to 3 miles off Kinmen and begun to supply the ROC with advanced weapons. The Chinese Communists considered the escorts a violation of the territorial waters of the People's Republic of China. On September 19, Soviet Premier Nikita Khrushchev sent a letter warning that the American actions threatened world war, claiming that the Soviet Union would be forced to honor its commitments to the territorial integrity of Communist China. The letter was rejected by the American government. The American Eisenhower Administration responded to the request for aid from the ROC according to its obligations in the ROC-United States mutual defense treaty that had been ratified in 1954. President Dwight D. Eisenhower ordered the reinforcement of the U.S. Navy Seventh Fleet in the area, and he ordered American naval vessels to help the Nationalist Chinese government to protect the supply lines to the islands. In addition, the U.S. Air Force deployed F-100D Super Sabres, F-101C Voodoos, F-104A Starfighters, and B-57B Canberras to Taiwan to demonstrate support for Taiwan. The F-104s were disassembled and airlifted to Taiwan in C-124 Globemaster II transport aircraft, marking the first time such a method was used to move fighter aircraft over a long distance. By September 11, the artillery crisis was overall stabilized (even though numerous rounds of artillery would still be fired by Communist China almost daily for the next two months or so) because U.S. Navy warships started to escort ROC convoys to Kinmen, breaking the previous artillery blockade due to constant PRC artillery shells that prevented any air or naval relief for Kinmen. The PRC did not want to risk war with the United States so they refrained from firing on any convoys if they observed U.S. Navy ships. The biggest issues in the crisis after September 11 were the air battles and the success or failure of the naval convoys relieving the Kinmen garrison. Also, under a secret effort called "Operation Black Magic", the U.S. Navy modified some of the F-86 Sabre fighters of the Nationalist Chinese Air Force with its newly developed early AIM-9 Sidewinder air-to-air missiles. These missiles gave the Nationalist Chinese pilots a decisive edge over the Chinese Communists' Soviet-made MiG-15 and MiG-17 fighters in the skies over the Matsu Islands and the Taiwan Strait. The Nationalist Chinese pilots used the Sidewinder missiles to score numerous kills on People's Liberation Army Air Force