Some said there were insufficient police to retake the streets from protesters who refused to be scared off by the tear gas. Others said the government bowed to public anger over the use of tear gas.

None of these arguments are too convincing. The Occupy Central movement has been brewing out in public for more than a year.

The most enlightening answer comes from a political veteran; the tear gas was not used to smoke out the students but to show Beijing's tough policy on Hong Kong and its loudest support for Chief Executive Leung Chun-ying.

The logic being the more the people take to the streets, the more nervous the state leaders are, and therefore the greater the support for a hardliner like Leung.

This is set against the background of a bitter power struggle in Beijing. Facing a purge that comes in the form of the anti-corruption campaign, no one will dare speak up for the moderate cause of Hong Kong. After all, it is better to be radical than to be wrong.

If that is indeed the game plan, the hardliners got what they wanted.

On October 2, the CCTV showed Leung's National Day speech in its evening broadcast. That used to be a privilege reserved for the Party Secretary.

On the same day, the front page of the published a commentary stressing the central government's "full confidence" in Leung. Again, normally only top leaders get that treatment.

The commentary said: "Judging from the political slogans and illegal demands posted by some in Hong Kong … their political goal is not the so-called 'genuine direct election' but a challenge to the country's top authority."

"The wrestling [over] political reform is not about having more or less democracy," said Chen Zuo-er, a former deputy director of the State Council's Hong Kong and Macau Affairs Office. "It is about the defence and seizure of the sovereignty over Hong Kong." Chen heads a national-level think tank.

To those who witnessed the 1989 political movement, this tone sounds all too familiar.

It is not many steps away from calling the protesters "counter-revolutionary" as Beijing did 25 years ago before sending in the tanks.

Next, why let the city's five busiest districts descend into anarchy? The violence that erupted last night perhaps provides the best answer.

Blocked streets with little sign of police presence ensures that the negative impact of the occupation on people's daily lives plays out to the full.

Toss in school closures, firemen complaining about ambulance delays and the delivery of rubber bullets by the police right in front of television cameras, and you have a powder keg ready to explode at the first spark.

When you have grannies shouting at youngsters trying to occupy Chai Wan, the fight in Mong Kok between the protesters and their opponents is no accident. Given the increasing public hostility, the occupation will soon peter out.

This is a strategy of "man against man, neighbour against neighbour", as the Bible says. Call this a success or not, Hong Kong will pay dearly for it.

First, with the last drop of trust gone, there is zero chance that Beijing will allow a more democratic electoral committee for the future chief executive election as some moderates are hoping.

Secondly, no pan-democrat will dare to make any compromise. Try tell the youngsters, who have spent nights in the streets and will be eligible for the next election, to vote for a compromiser.

Settlement of the political system debate and therefore a pullback from the impasse is out of the question. What is sadder is the polarisation among Hongkongers increased by these clashes. Brothers and sisters quarrel on whatsapp. Long-time friends "unlike" each other on Facebook. Dim sum family gatherings turn silent to avoid the sensitive subject.

Hong Kong will never be the same.