China and Portugal signed the Sino-Portuguese Treaty of Peking (《中葡和好通商條約》) in 1887. However, it left the Macao’s (Macau) boundary issue unsettled, which became a decades-spanning Sino-Portuguese diplomatic challenge. Disputes over Macao’s maritime boundaries emerged when the Canton Custom collided with the Portuguese Macao government in the former’s operations against smugglers and pirates in the early 20th century. Meanwhile, the Portuguese Macao government’s large-scale land reclamation projects near Macao’s Inner Harbour for boosting trade provoked China. The Guangdong (廣東) Constitutional Protection Junta took the initiative to approach the Portuguese Macao government for negotiations over the Macao’s boundary issue in 1919. Portugal even submitted the issue to the Washington Naval Conference for international arbitration. However, the issue was shelved as negotiations ended in deadlock.

The Governor of Macao José Carlos da Maia requested the Portuguese embassy in Beijing (北京) in 1914 to carry out a boundary survey to proceed the construction projects in Macao’s port and settle Macao’s maritime boundary issue.

Sun Baoqi (孫寶琦), the Foreign Minister of the Republic of China. Sun met with the Portuguese Minister to China, J. Batalha de Freitas, in 1914. Both sides agreed to solve the Macao’s boundary issue as soon as possible.

Postcards featuring the land reclamation projects in Macao in the early 20th century. China opposed the projects in fear that the Portuguese Macao government would expand its controlled areas by reclamation when Macao’s land and maritime boundaries were undetermined. (Collection of Mr. Lei Kun-min, Macao In Postcards, 19th & 20th Centuries, published by Macao Association for Historical Education, cited from “Macau Memory”, Macao Foundation)

Two photos of Changdi Road (長堤大馬路), Guangzhou (廣州), featuring the Canton Customs building in the Republican era. During this period, the Canton Customs and the Portuguese Macao government frequently clashed over the former’s anti-smuggling operations.

The waters near Macao were fraught with pirates (photoed) and smugglers during the Republican era. Sino-Portuguese clashes emerged during law enforcement operations.

Wu Chaoshu (伍朝樞), the Deputy Foreign Minister of the Guangdong Constitutional Protection Junta. Wu and the Consul General of Portugal in Guangzhou negotiated the Macao’s boundary issue in 1920.

Henrique Monteiro Correia da Silva dealt with the Macao’s boundary issue during his tenure as the Governor of Macao between August 1919 and January 1923.

The 1921 Washington Naval Conference brought together the United States, Britain, Japan, France, Italy, the Netherlands, Belgium, Portugal, and China. On the top of the agenda were two subjects: limitations of naval armaments and problems in the Pacific Ocean and the Far East.

The Chinese chief delegate on the conference was Shi Zhaoji (施肇基) and the Portuguese chief delegate was José Francisco de Horta Machado da Franca, Viscount of Alte. The Portuguese delegates proposed to arbitrate the dispute over Macao’s boundaries.

The conference designated Leonard Wood, the Governor General of the Philippine Islands, as the arbitrator. Still, no conclusive statement was made on Macao’s boundaries.

Photo courtesy of Mr. Alex Lou, Vice Chairman of The Heritage Society (pictures 1 and 7), Macao Foundation (picture 3), Fotoe (pictures 2, 4, 8, and 9), and misc. photo sources.