The real tragedy of China’s gradual erasure of Hong Kong’s relative freedom and rule of law is that it is rooted in geography and history and hard to reverse.

The British owned Hong Kong Island since the First Opium War (1839 – 42), but it was crowded around Victoria Peak, so they added mainland Kowloon in 1860 after an Anglo-French military expedition burned down Beijing’s Summer Palace in the Second Opium War. Needing more space, Britain leased the much-larger New Territories in 1898 for 99 years. The New Territories (which include Lantau Island, where the new airport opened in 1998) provides Hong Kong’s water, and Beijing would not renew the lease.

Britain had no choice but to return all of Hong Kong in 1997, covered by the fig leaf that it was to be a “special administrative region” (SAR) with its own economy, laws and currency for 50 years. Portugal handed back Macau under a similar deal in 1999. Touted as “one country, two systems,” it soon became apparent that Beijing was not going to wait 50 years to absorb Hong Kong, which it is doing slice by slice.

Look for China to add these slices: Order Hong Kong to drive on the right instead of British-style on the left. Adopt modern, simplified Chinese characters, in use on the mainland since the 1950s, replacing traditional characters used in Hong Kong and Taiwan. Compulsory teaching of Mandarin as opposed to Cantonese in Hong Kong and Macau.

The British never implemented democracy in Hong Kong. When Hong Kongers began to demand it, Beijing told the Brits not to, and they didn’t. At present, a 70-member Legislative Council (LegCo) is chosen by a rigged system that chiefly represents the wealthy and powerful. Fearing for their economic interests, the LegCo does not oppose Beijing’s creeping takeover.

The latest slice is an “extradition” agreement the LegCo was to pass to let China grab up anyone in Hong Kong for trial in the mainland. This is a largely symbolic last straw, as China has been abducting critics for years, including Hong Kong booksellers. Hong Kongers oppose tyranny, but demonstrations are about all they can do. As many as 2 million recently protested the extradition measure, thronging swish boulevards. Handpicked SAR chief executive Carrie Lam obeys Beijing, but a nervous business community made her temporarily back down.

Xi Jinping can neither show weakness nor crack down too hard. As elsewhere, Beijing applies subtle, incremental tactics. First, let anti-mainland Hong Kongers depart. Get rid of dissidents early. Many already have settled in Vancouver, whose housing prices have soared.

Another exodus from Hong Kong may damage its financial reputation, but that’s fine with Beijing. Before World War II, Shanghai, not Hong Kong, was China’s financial center, a status Beijing aims to reclaim. A few years ago, one top party official said Shanghai will be China’s “New York” and Hong Kong its “Toronto.” Actually, the net winner is likely to be Singapore; it has the location (outside China), language skills and rule of law that attract global businesses.

Beijing tames Hong Kong’s free media by having firms withdraw advertising from critical media, who get the warning and knuckle under. Hong Kong’s South China Morning Post was long one of the best newspapers of East Asia, but its independence is now clouded. Expect Beijing to block international social-media platforms in Hong Kong and replace them with China’s state-run platforms, sealing Hong Kong behind the Great Firewall.

The marches rebuke Xi. Good. He could order gunfire, but a Tiananmen-type massacre would shatter the stable authoritarianism China showcases. Incorporating Hong Kong, however, risks Hong Kongers spreading democratic demands into a China that faces a slowing economy, unpay-able debt, corruption and discontent.

A principled U.S. stand supporting Hong Kong’s freedoms could jolt Beijing at the right time, prodding reforms. Ending Hong Kong’s special trade status separate from China might get Beijing’s attention. President Trump, however, does “deals,” not principles. Congress urges human rights in China, but Trump, set to meet Xi at the G20 this week, ignores the calls, hoping Xi ends the trade war and buys more American soybeans.

Beijing hoped “one country, two systems” would lure Taiwan back to the mainland, but Taiwanese, who have enjoyed lively democracy since the 1990s, reject the con. When Washington established full diplomatic relations with Beijing in 1979, a Republican-backed U.S. law supported Taiwan but promised nothing specific.

Now is the time to announce measures that convey democratic and human-rights values. True, this may have little immediate impact and anger China. A mute America, however, signals U.S. timidity and weakness and tells Beijing they may act with impunity, bad news for the future not only of Hong Kong but of Taiwan and the Asia/Pacific generally. Few suppose China will rest content with the China Seas.