It isn't true the "only" reason Hong Kong is a part of the PRC is because they agreed to that declaration. This agreement was made because PRC could unilaterally annex Hong Kong at anytime.
But they didn’t. An agreement was reached.
“I could have walked away, but didn’t” isn’t a valid reason for breaking a deal.
What we’re seeing now is even just that extremely minor inconvenience is too much for Xi. He could get China everything he wants just by waiting. But he would rather tear up a signed treaty than wait.
The key is that HK was very useful as a gateway with the rest of the world for import/exports and finance. They preserved it because, while they despised foreign presence, it served their interests to. Iirc, at one point something like 90% of the PRC's imports and exports transited via HK.
China would have immediately faced sanctions and the possibility of military support to dissident movements within its borders. Not to mention, accelerated arms sales to its neighbours.
They could not have cared less about 'sanctions', which seem like a meaningless threat at the time of the Cold War and Maoist China.
The West was and still is supplying weapons to their neighbours, which is not very important, anyway.
As for 'dissident movements'... This is not a South American banana republic. The CIA probably did try things at some point but clearly to no effect because there is no 'dissident movement' of any scale.
From a historical point of view the question I am very interested in is why did Mao stop short of retaking Macao and HK, and of taking Taiwan in 1949?
They refrained from taking Russian colonial possessions in the North, which is understandable. But I am puzzles about the rest.
For HK and Macao, perhaps he wanted to respect treaties because he also wanted to rely on treaties regarding Tibet (which all the powers recognised as Chinese by previous treaty), I don't know.
Mao was long dead when the relevant treaties were negotiated.
> CIA probably did try things at some point but clearly to no effect because there is no 'dissident movement' of any scale
In the late 90s, the West best over backwards to accommodate China. It was a new market and stable Asian power.
Modern China has dissident and separatist movements. The NPC has prioritised legislation precisely to head off the threat. Censors scrub the Hong Kong and Tianamen Square protests for similar reasons.
> why did Mao stop short of retaking Macao and HK, and of taking Taiwan in 1949?
He didn’t have the firepower. Water crossings are taxing. It would have taken a full military commitment, and still left the endpoint uncertain. Consolidating power on the mainland was the more prudent move.
We're discussing the option communist China had to take HK back by force. The point is thus why that did not occur in 1949 or the 50s.
That is a long time, 156 years from 1997 is 2153.