Upvote:-1
Piece by piece, part by part, the British took over much of the world. And they often took power as the "puppet master". Often, the British play 'games' played with legalism as a prelude to explicit political control.
India, for example, didn't legally become a British colony until 1858. However, the British controlled much of India and its economy since the 1750's. Between 1750 and 1859, the Moguls were legally in charge. So it took 100 years from economic control to political control.
Egypt, as another example, was controlled by the British from 1882 until at least 1952 with the rise of Nasser's popular leadership. However, Egypt until 1914 was a province of the Ottoman empire. There were a variety of legal arrangements after 1914. The point is that the British empire often gained and held colonial power without legal colonial status.
The 99 years from 1898 to 1997 featured geopolitical changes that were impossible to predict. A 1898 Britisher would probably have assumed that China would be completely dismembered and under colonial control by 1980, so the idea of a 99 year lease expiring might have been view as nonsense.
I do have another answer in the SE History question about why China wasn't subjugated by European colonialism. This might also be relevant.
Upvote:2
There were (at least) two reasons.
The first was that there was no "provocation" from China in 1898. The British took Hong Kong Island in 1842 after the Opium War, and Kowloon in 1860 after the Arrow War, which is sometimes referred to as the Second Opium War. There was no war (with China) in connection with the acquisition of the New Territories. Given this absence, and the fact that the New Territories were 12 times larger than the rest of Hong Kong, an outright annexation would have appeared overly greedy. The British, in this instance, preferred to "rule by proxy" by leasing it for 99 years.
A second, and related reason, was that unlike the other two annexations, the acquisition of the New Territories was not a move against China, but primarily a move against other European countries. Britain, at that time, was more interested in trade in China than anything else. Unlike the earlier periods, an annexation of Chinese territory in 1898 might have led to "a scramble for colonies" like the one that had recently taken place in Africa. Britain (and the United States) preferred (nominally) "equal access" to all of China, as opposed to "special privileges" (compared to European countries) in part of China and exclusion from the rest.
Basically, an outright annexation of the New Territories would probably have had a lot of unintended consequences, while a 99-year lease appeared to serve the same purpose while being less overtly aggressive, or at least push the problem far enough into the future so that another generation would have to deal with it. And, according to Wikipedia:
"Lord Lugard was Governor from 1907 to 1912, and he proposed the return of Weihaiwei to the Chinese government, in return for the ceding of the leased New Territories in perpetuity. The proposal was not received favourably, although if it had been acted on, Hong Kong might have remained forever in British hands."
This proposal was not adopted because the British preferred to keep Weihaiwei (in Shandong) as a check against the Germans in nearly Tsingdao, and the Russians in nearby Port Arthur. No one at the time thought that China would be the main concern regarding Hong Kong in 1997.