In 1842, the Qing court (清朝) and Britain signed the Treaty of Nanking (Treaty of Nanjing, 《南京條約》), which stipulated the cession of Hong Kong Island and the opening of five treaty ports. To salvage Macao (Macau) from the consequent strike of trade status, Portugal demanded similar treatment as Hong Kong and friendlier trade regulations. Giving the fruitless negotiations with the Qing Imperial Commissioner Qiying (耆英), the Portuguese opted to colonise Macao by force.

Portugal appointed João Maria Ferreira do Amaral as the Governor of Macao in 1846. Under his iron fist rule, the Portuguese Macao government’s administration expanded from the Macao city, outside the city, to the whole Macao Peninsula. However, Ferreira do Amaral’s harsh colonial rule sparked a backlash. He was assassinated by Shum A-mai and his fellow villagers in 1849.

Knowing that its colonial rule over Macao lacked legal justification, Portugal thus pushed the Qing court to recognise the cession of Macao. When the Anglo-French forces conquered Beijing (or Peking, 北京), the French envoy to China arranged negotiations between the Qing court and the Governor of Macao Isidoro Francisco Guimarães in Beijing in 1862. The negotiations were concluded by drafting the Sino-Portuguese Treaty of Friendship and Trade (《中葡和好貿易條約》). However, the Qing court refused to ratify the treaty in 1864 when certain terms were found violating China’s sovereignty over Macao.

China and Portugal negotiated on anti-smuggling and taxation regarding opium in 1886. The negotiations resulted in signing the Sino-Portuguese Treaty of Peking (《中葡和好通商條約》), stating that China confirmed the Portuguese perpetual occupation and government of Macao, but Portugal could never alienate Macao and its dependencies without China’s agreement. However, the treaty did not fully solve the Macao issue. Given Portuguese expansion into the Macao Peninsula, and the islands of Taipa and Coloane at the late 19th century, the controversy over the Macao boundaries was then brought to the negotiation table.