IT WAS BOUND to be an anxious year for the Chinese Communist Party. Years ending in 9 have always been since the crushing of the Tiananmen Square protests on June 4th 1989. The party feared that anniversaries of the bloodshed might trigger unrest (though security is always so tight that they never have). In 2019 they were on heightened alert, jittery not only about the 30th anniversary, but about other round-number anniversaries of political upheavals, including a national one a century ago, another in Tibet, and the party’s own seizure of power in 1949.

But China’s leader, Xi Jinping, was right to sense that troubles in 2019 might come from unexpected quarters. In a speech in January he warned officials of “black swan” and “grey rhino” events, in other words, unforeseen crises or ones arising from obvious but neglected problems. What occurred was a combination of both types, with the colour black prevailing. It was in Hong Kong that the year’s biggest crisis erupted, on a scale that caught not only the party, but the entire world, by surprise. Chinese officials call it a colour revolution, or, referring to the preferred hue of anti-government protesters involved in it, a black terror.

The unrest that erupted in the territory in June has been the biggest sustained challenge to the party’s authority since the upheaval of 1989. The central government in Beijing says the demonstrations have transgressed the “bottom line” of the “one country, two systems” principle that China says it has been implementing in Hong Kong since it took it back from the British in 1997. Despite such rhetoric, the party has refrained from sending in troops to crush the protests. But the challenge it faces is far from over. Despite widespread violence, public support for the protesters still appears strong. Mr Xi may continue to keep his troops leashed, but he will find other ways of tightening control in the territory.

Hong Kong’s protests have complicated China’s already deeply troubled relations with the United States. Officials in Beijing have reacted furiously to support for the protesters from American politicians. President Trump, focused on fighting his trade war with China, has been more reticent, but after Congress gave overwhelming approval to bills aimed at improving human rights in Hong Kong, Mr Trump in November signed them into law. He may do the same again soon with a bill that would require him to impose sanctions against Chinese officials guilty of human-rights violations in the far-western region of Xinjiang. A senior leader in Xinjiang recently said people who had been studying in “vocational training” schools there (ie, Muslims confined without trial in a vast gulag) had all “graduated”. But it is a safe bet that anyone released will remain under close watch.

The repression in Xinjiang, and China’s resolute opposition to democratic reform in Hong Kong, are being closely watched in Taiwan, where presidential and parliamentary elections will be held on January 11th. It is likely that voters will react by giving more support to Tsai Ing-wen, who, before the outbreak of unrest in Hong Kong, had been widely expected to lose her bid to serve a second term as president. A victory for Ms Tsai and her independence-leaning party would infuriate Mr Xi, who sets great store by the “great rejuvenation of the Chinese nation”—meaning, among other things, reunification with Taiwan.

China is not likely to risk conflict with America in 2020 by attacking Taiwan, but cross-strait tensions will rise. Mr Xi used one of 2019’s big anniversaries, the 70th of Communist rule that was marked on October 1st, to show off the kind of weaponry that China might use should it ever come to blows with America. The intended message of the big parade in Tiananmen Square was clear: Mr Xi remains firmly in charge, with the world’s largest army at his command. Despite all the pressures he endured in 2019, there is no clear evidence to the contrary.