Hit squads, assassinations and violent strikes.
In explaining why the film To Singapore, With Love was deemed a security threat, Minister for Communications and Information Yaacob Ibrahim took members through a violent period of Singapore's history.
"From 1948 onwards, over four decades, the Communist Party of Malaya (CPM) waged a determined campaign using violence and subversion to install a communist regime in Malaysia and Singapore," he said, adding that communist hit squads assassinated Singaporeans in broad daylight.
But the CPM also used Communist United Front tactics to infiltrate and take control of open organisations like student bodies, labour unions, political parties and cultural organisations.
"They used these organisations to foment demonstrations, strikes and riots. They sought to destabilise the country and establish a communist state through illegal means."
The film, he said, contains untruths and deception about history.
Therefore, it was assessed by the censors to undermine national security and received an appropriate classification.
Last month, the Media Development Agency (MDA) rated the documentary on political exiles "not allowed for all ratings", which prevents the film from public screenings.
But it is allowed for screening for educational purposes, subject to the film-maker's consent.
For instance, MDA had recently agreed to a request from Yale-NUS College to screen To Singapore, With Love in a course on documentaries about conflicts.
But how is the film a national security threat, asked MP Zaqy Mohamad and newly-elected nominated MP Kuik Shiao-Yin.
The documentary has been featured at film festivals in Busan in South Korea, Taiwan and London.
On Sept 19, about 350 Singaporeans organised a trip to Johor Baru, Malaysia, to catch the film.
Dr Yaacob said the film "obfuscates and whitewashes" an armed, illegal organisation, and violent and subversive acts directed at Singaporeans. A public screening of the film would mean condoning them.
The film would also erode public confidence in the Government on security matters, he added.
He said: "Not to take any action against films which contain distorted and untruthful accounts would give the wrong impression that there is truth to their claims and that the Government's actions against these individuals were unwarranted."
He pointed out that the documentary by director Tan Pin Pin portrayed a "misleading account" of the exiles' pasts designed to evoke sympathy and support for them.
Several of those featured in the film were members of the CPM.
Dr Yaacob said: "These individuals had been involved in violent and subversive actions to advance the CPM's agenda, and had posed a serious threat to the security of Singapore and the safety of Singaporeans.
"They chose to leave Singapore to avoid being held accountable for their actions."
Ms Tan re-submitted her film unchanged on Sept 30.
The film-maker had previously expressed her disappointment over MDA's decision and said the film focused on their everyday lives.