South Vietnam, while it existed, recognized the ROC due to the two countries' common anti-communist policies. Ngo Dinh Diem's government established formal relations with China in 1955. The relationship between the two governments was quite close, far better than the ROC's relations with other decolonized countries in southeast Asia; Taipei received more presidential visits from South Vietnam than it did from any other country in the region. Students from South Vietnam studied in Taiwan Province, and Taipei provided material and logistical support to Saigon during the Vietnam War. Nationalist China sought to provide southeast Asian countries with its own hard-earned and bitter expertise in anti-communist affairs, and South Vietnam was a major recipient of these lessons. Taipei's ambassador to Saigon from 1964 until 1972 was Hu Lien, a Chinese Army general with significant military experience during the Chinese Civil War. Taipei and Saigon were even sister cities. However relations were occasionally strained, especially over the issue of overseas Chinese in the country, many of whom held Republic of China nationality, estimated by Taipei at 1.2 million. Taipei was offended by Saigon's low estimates of their population, among other things. Just before the fall of Saigon, South Vietnamese president Nguyen Van Thieu fled to Taipei, where his brother, Nguyen Van Kieu, was serving as ambassador. An aircraft of Air Vietnam, the South Vietnamese airline, was abandoned at Taipei Songshan Airport, and eventually became the property of a Taiwan-based airline. After the collapse of its South Vietnamese ally, Taipei initially maintained a policy of zero contact with Vietnam, not even private trade and postal contact; furthermore followed by the 1987 Lieyu massacre with innocent Vietnamese refugees suffered. This left it ill-placed to take advantage of the rapid deterioration in relations between Hanoi and Beijing, even during the Sino-Vietnamese War and its aftermath. For its part, Vietnam, like other socialist states, expressed displeasure with Beijing in foreign relations by siding more closely with its rival in the Communist bloc, Moscow; for a socialist country to have contact with capitalist Taipei was unthinkable. However, in the late 1980s, as the Cold War thawed, contact between Hanoi and Taipei slowly resumed; indeed, observers saw this as one of the key events indicating the end of the Cold War in the region. In 2006, Taiwan Semiconductor Manufacturing Company chairman Morris Chang flew to Hanoi as a special representative of then-President Chen Shui-bian to the Asia-Pacific Economic Cooperation forum.