Refugee operations were organized through the Santa Casa da Misericordia. Unlike in the case of Portuguese Timor, which was occupied by the Japanese in 1942 along with Dutch Timor, the Japanese respected Portuguese neutrality in Macau, but only up to a point. As such, Macau enjoyed a brief period of economic prosperity as the only neutral port in South China, after the Japanese had occupied Guangzhou (Canton) and Hong Kong. In August 1943, Japanese troops seized the British steamer "Sian" in Macau and killed about 20 guards. The next month they demanded the installation of Japanese "advisors" under the alternative of military occupation. The result was that a virtual Japanese protectorate was created over Macau. When it was discovered that neutral Macau was planning to sell aviation fuel to Japan, aircraft from the "USS Enterprise" bombed and strafed the hangar of the Naval Aviation Centre on 16 January 1945 to destroy the fuel. American air raids on targets in Macau were also made on 25 February and 11 June 1945. Following Portuguese government protest, in 1950 the United States paid US$20,255,952 to the government of Portugal. Japanese domination ended in August 1945. When the Chinese communists came to power in 1949, they declared the Protocol of Lisbon to be invalid as an "unequal treaty" imposed by foreigners on China. However, Beijing was not ready to settle the treaty question, leaving the maintenance of "the status quo" until a more appropriate time. Beijing took a similar position on treaties relating to the Hong Kong territories of the United Kingdom. In 1951, the Salazar regime declared Macau, as well as other Portuguese colonies, an "Overseas Province" of Portugal. During the 1950s and 1960s Macau's border crossing to China Portas do Cerco was also referred to as "Far Eastern Checkpoint Charlie" with a major border incident happening in 1952 with Portuguese African Troops exchanging fire with Chinese Communist border guards. According to reports, the exchange lasted for one-and-three-quarter hours, leaving one dead and several dozens injured on the Macau side and more than 100 casualties claimed on the Communist Chinese side. In 1954, the Macau Grand Prix was established, first as a treasure hunt throughout the city, and in later years as a formal car racing event. In 1962, the gambling industry of Macau saw a major breakthrough when the government granted the "Sociedade de Turismo e Diversões de Macau" (STDM), a syndicate jointly formed by Hong Kong and Macau businessmen, the monopoly rights to all forms of gambling.