The pro-democracy demonstrations in Hong Kong are the story of the hour, in my book. Hong Kong is important itself (it has 7 million people). But what’s happening there is a test of the future of freedom for China’s billions.

Without which — mark it well — eventually there will be a war.

My own appreciation for that danger was gained during the 1970s, when I was posted in Hong Kong for The Wall Street Journal. In 1984, with end of Britain’s lease on most of the colony but 13 years away, Britain and China signed their Joint Declaration.

This promised democratic reforms (“one country, two systems”), including universal suffrage in Hong Kong by 2017. Even so, the Journal urged Britain to take a hard line by holding out for Hong Kong Island, to which Britain owned title in perpetuity (like the Falklands).

That argument infuriated Prime Minister Margaret Thatcher. She vented this when she visited the paper’s editors in 1990, calling the editorials “hurtful.” Then she leaned her capacious bosom forward, stared at the editor across the table, and demanded: “Do I make myself cleee-ah?”

I’d left the Journal by then, but Dan Henninger tells me Bob Bartley didn’t bat an eyelash. He just flashed “one of the largest Bartley Cheshire Cat grins of all time.” Nor did the paper back off.

Both Thatcher and Bartley have left this mortal coil, but the promises China made during those years are what is being tested today. Students are risking their lives to redeem the guarantees. Their protest ranks with the pro-democracy demonstrations that erupted in 1989 at Tiananmen Square.

That’s when a lone protester faced down a column of tanks of the Red Army. It was one of the most astonishing pictures of individual courage ever filmed. During Tiananmen, incidentally, more than 1 million people came into the streets of Hong Kong to show solidarity.

Yet Hong Kong could prove more important than Tiananmen. This is because if freedom comes to China, it is going to enter through Hong Kong. The city already had its taste of liberty, if only a taste, and it just is never going to forget.

The reason this is coming to a head now is that the Red Chinese have been breaking their promises. What they mean by universal suffrage, The Post pointed out this week, is that everyone gets to vote for candidates approved by the Communist camarilla.

Journalists and editors are being beaten, judges — famously independent under Britain — are being harangued to be “patriotic” to the Communist line.

And a major civil servant has reportedly just admitted in court he’d received a $1.3 million payoff from “Beijing,” as the Communist capital is known.

This is a moment to remember that the West has its own obligations in Hong Kong. The point was made last month in The Financial Times by the last British governor of Hong Kong, Chris Patten (who had famously wept when Hong Kong was handed over to the Communists).

Patten wrote that he wanted to “invite an interrogation of Britain’s sense of honor.” The United Kingdom, after all, was a party to the Joint Declaration, the treaty under which the Communists guaranteed to preserve Hong Kong’s way of life for 50 years after 1997.

America has its own obligations. The United States-Hong Kong Policy Act of 1992 requires our government to report regularly on Hong Kong’s progress.

It has done a sporadic job of that at best — partly because Congress recently failed to fund the report, and then-Secretary of State Hillary Clinton didn’t seem to care.

And several months ago, two of Hong Kong’s tribunes of democracy — Martin Lee, founding chairman of its Democratic Party, and Anson Chan, a former chief secretary of Hong Kong — came to Washington to remind America of its obligations.

The Obama administration palmed them off on Vice President Joe Biden.

All in all, it’s hard to imagine, at this point, that President Obama will lead on China.

That in and of itself deserves to become an issue in the runup to the 2016 election. Natan Sharansky likes to say that war doesn’t break out between democracies.

If the Chinese Communist Party can’t tolerate democracy in Hong Kong, where in China will it ever be found — and how will China’s designs on the world be tempered?

Do I make myself clee-ah?

This column original appeared in the New York Post.