Zhou Yongkang, the big “tiger” caught in the anti-corruption campaign in China, was sentenced to life in prison on June 11 at a secret trial, after a series of developments that have attracted the attention of the world public over the past two years.

Here are five things to know about what has been described as China's biggest case in at least 40 years.

Who is Zhou Yongkang?

Zhou Yongkang in his last public appearance in October 2013 (Photo: Xinhua).

Mr. Zhou, 73 years old, was the head of security agencies in China, a former member of the Politburo Standing Committee, the supreme leadership body of the Communist Party of this country.

A feared figure known for his angry countenance, Mr. Zhou rose through China's oil industry before taking up his post as minister of public security and head of the Communist Party's Central Political and Legal Affairs Commission, overseeing all domestic security issues, from police and courts to prisons and domestic surveillance.

In 2012 Zhou Yongkang retired.

When was Zhou Yongkang suspected?

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Zhou Yongkang's enormous influence in Chinese politics and in the oil and gas business world (Photo: BBC)

Speculation that Mr Zhou might be in trouble arose when a political ally, Bo Xilai, was sentenced to life in prison for corruption in September 2013. Mr Zhou was last seen in public a month later.

Since then, Zhou’s family members and close associates have drawn the attention of anti-corruption agencies. In July last year, Zhou Yongkang was formally placed under investigation for “serious violations of discipline,” before being formally prosecuted for corruption in April 2015.

What crime did Zhou Yongkang commit?

Zhou Yongkang with white hair in court on June 11, 2015 (Photo: CCTV).

After a secret trial in Tianjin city, Mr. Zhou was convicted of corruption, abuse of power and revealing state secrets.

The former official, his wife and son accepted bribes in cash and property worth 129.8 million yuan ($21 million), the court said. The beaten “tiger” ordered some of his subordinates to help family members and others illegally profit from 2.1 billion yuan. Zhou also gave six confidential documents to a businessman, the court said.

China's most serious case since 1976

To date, Zhou is the highest-ranking and most powerful Communist Party official to be tried and imprisoned since the Gang of Four case in 1976. Over the past three decades, no Politburo Standing Committee member, current or retired, has been prosecuted.

What does Chu's "fall from the horse" signal?

The sentencing of Zhou Yongkang further cements President Xi Jinping's image as China's most powerful leader in recent years, and is a milestone in Xi's long-running fight against corruption.

However, the secrecy of the trial has caused many foreign journalists and experts to express skepticism about Beijing's commitment to the rule of law.

(According to Dan Tri)