Zhou Yongkang, a major figure caught in China's anti-corruption campaign, was sentenced to life imprisonment on June 11th in a secret trial, following a series of events that have drawn worldwide attention over the past two years.

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

Who is Zhou Yongkang?

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

Mr. Chu, 73, was formerly the head of China's security agency and a member of the Politburo Standing Committee, the top leadership body of the Communist Party of China.

A feared figure known for his angry demeanor, Zhou rose through the ranks of China's oil industry before becoming Minister of Public Security and head of the Central Political and Legal Affairs Commission of the Communist Party of China, overseeing all aspects of national security, from the police and courts to prisons and domestic surveillance.

Zhou Yongkang retired in 2012.

When did Zhou Yongkang first become the subject of suspicion?

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Zhou Yongkang's immense influence in Chinese politics and the oil and gas industry (Photo: BBC)

Speculation about potential trouble for Zhou emerged when a political ally, Bo Xilai, was sentenced to life imprisonment on corruption charges in September 2013. Zhou's last public appearance was a month later.

Since then, family members and close associates around Zhou began attracting attention from anti-corruption agencies. By July last year, Zhou Yongkang was officially investigated for “serious disciplinary violations,” before being formally charged with corruption in April 2015.

What crime did Zhou Yongkang commit?

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

Following a closed-door trial in Tianjin, Mr. Zhou was convicted of corruption, abuse of power, and leaking state secrets.

The former official, along with his wife and son, received bribes in cash and assets totaling 129.8 million yuan (US$21 million), the court asserted. The disgraced "tiger" ordered several subordinates to assist family members and others in illicitly profiting 2.1 billion yuan. Zhou also handed over six confidential documents to a businessman, the court confirmed.

The most serious case in China since 1976.

To date, Zhou is the highest-ranking and most powerful Chinese Communist Party official to be tried and imprisoned since the 1976 "Gang of Four" case. For the past three decades, not a single member of the Politburo Standing Committee, current or retired, has been prosecuted.

What does Chu's downfall foreshadow?

The conviction of Zhou Yongkang further solidified President Xi Jinping's image as China's most powerful leader in recent years and marked a significant milestone in his long-running anti-corruption campaign.

However, the fact that the trial was held in secrecy has led many foreign journalists and experts to express skepticism about Beijing's commitment to the rule of law.

(According to Dan Tri newspaper)