Hong Kong was ceded to the British Empire in 1841 following Opium Wars. The colony would serve as stopping point for Western ships traveling to China for the next 100 years. During the Second World War, Hong Kong was bombed and invaded on Christmas Day 1941 and subsequently liberated at the end of the war. After the defeat of the nationalist forces in the Chinese Civil War, many mainland Chinese took refuge in Hong Kong. Despite the United Kingdom recognizing the People's Republic of China, there were still tensions ongoing with the PRC on the case of abduction of Hong Kong citizens in China.
Macau, just situated to the west of Hong Kong, was a Portuguese colony and one of it's last colonies in the Far East.
While sparred from the bombs that hit the mainland, both Hong Kong and Macau lost contact with their mother nations.
Great Nuclear War
Hong Kong, consisting of Hong Kong Island, Kowloon, and the New Territories, quickly set about with reforms to allow itself to survive. However, by 1963, tensions had been built after a rogue PLA unit, without orders from the Central Military Commission in Beijing, begun raiding the local area, frequently taking supplies from Kowloon. Although the British Overseas Forces managed to chase them out of the territory, the drain resources and manpower put a strain on the local defenders as casualties mounted. Without the military to fight these, Hong Kong leaders met with the Commander of the unit in 1964. Discussions began, and a loose agreement was made: The PLA Unit would defend and assist Hong Kong, and in return Hong Kong would house and give supplies to the unit.
Over time, this arrangement evolved into the Unit becoming more of an official army, with local residents joining the army. By 1968, Hong Kong began to expand slightly into the mainland. The territory continued to do so over the next 7 years.
Contact with Macau and Hainan
However, in 1975, contact was made with the City of Macau. Macau was barely surviving, and was often attacked by marauding PLA units. The leaders of the two cities met, and after a week of discussions, a decision was made: Macau and Hong Kong would unite for the Commonwealth of these two nations and the pooling of resources. On the 23rd July, the Commonwealth of Hong Kong and Macau was declared. This new nation consolidated its power, while expanding slightly to the mainland, and establishing territory to connect them.
On 19th February 1987 a small Hong Kong-Macau landed on Hainan, which had collapsed into chaos since the Great Nuclear War. Originally the waters around the Island protected it from refugees, but it also prevented supplies and trade. By 1987 order was scarce and the population had fell dramatically. The only semblance of governance was in the capital city of Haikou. Hong King-Macau immediately aided Hainan, and met with the leaders of Haikou. With many discussions lasting almost two weeks, it was decided that Hong Kong-Macau forces would land in Hainan and assist Haikou in asserting control over the island, and in return Hainan would become a part of the Commonwealth. This was intended to be a temporary measure.
A New Republic
Discussions between many parties lasted the remainder of 1987, and it was eventually decided a new form was needed for the country. On the 1st January 1988, the Republic of the Pearl Delta was proclaimed, officially the Republic of Zhusanjiao. The new state, still based in Hong Kong, was somewhat decentralised, and was warmly received.