JAKARTA, Indonesia — It's difficult to overstate the role that anti-communism plays in today's Indonesia . An attempted coup in the mid-1960s triggered a military purge against communists, leaving somewhere between 500,000 and 1 million people dead and paving the way for three decades of dictatorship.

Today, communism is banned across the country, but the events of the five decades ago have remained in the collective psyche of this archipelago nation in Southeast Asia. During the rule of Gen. Suharto, who became president in 1967, the government explained the massacres as necessary to rid the country of communism. Since Suharto's resignation in 1998 and the introduction of democracy, however, public pressure has steadily grown to explain what the CIA has labeled one of the worst mass murders of the 20th century, according to Mark Aarons.

This fall, protests and a rally have dredged up a decades-old dormant anxiety over communism. Analysts say those events are less about a fear of communism and more about deeper tensions in politics and civil liberties. Additionally, they suggest that many aging military leaders are worried about the fast-approaching 2019 presidential elections and efforts to reassert themselves in the civilian national government, analysts say.

Observers also say the September events – two gatherings dedicated to remembering the mass killings of the 1960s that were disrupted and a rally against communism – have put a spotlight on today's political scene in Indonesia, an unstable landscape punctuated by the growing role of Islamist groups and whose roots include U.S. government involvement during the Cold War. Those roots were partly exposed in mid-October by new declassified files from the U.S. State Department that describe how American officials kept track of the mass killings of the 1960s .

The current anti-communist revival reveals "how the effects of the U.S.-assisted mass killings of 1965-66 continue to destabilize Indonesian democracy," says Reza Muharam, who leads the International People's Tribunal to demand government recognition for the 1965-66 killings.

In September, protesters disrupted two events discussing the history of the 1965 mass killings, featuring survivors of the military campaign, at the Jakarta Legal Aid Institute. A week later, there was a mass rally outside the Jakarta House of Representatives that attracted 15,000 protesters under the banner of "reject the PKI," as the Communist Party of Indonesia is known here.

In both these cases, anti-communist protesters joined forces with Islamist groups that rose to unusual prominence during the past year. The hardline Islamic Defenders Front, the most prominent of these groups, was present at the protests and the rally. The rally, in particular, made use of the Islamists' well-oiled protest infrastructure, and looked very similar to last year's mass prayer demonstrations against Basuki "Ahok" Tjahaja Purnama, Jakarta's Christian governor.

Visitors take photos near a memorial to the seven army officers who were killed in an abortive coup in 1965 that the military blamed on Indonesia's Communist Party and subsequently led to the anti-communist purge in 1965-1966, at Pancasila Sakti Monument in Jakarta, Indonesia on Oct. 15, 2017. (Dita Alangkara/AP)

The anti-communists and Islamists are both allied with a larger, third force that is ultimately driving much of their current resurgence: the military. "Anti-communism is strongest in the military and among pious Muslims," says William Liddle, an Indonesian politics expert at Ohio State University.

Observers say the military is restive now partially because President Joko "Jokowi" Widodo's first term is past its halfway mark, and military affiliates are already eyeing the 2019 election. Jokowi is the first Indonesian president without a defense background, and the military has often taken a combative stance against the executive branch during his term. In 2014, Jokowi narrowly beat a prominent army general, Prabowo Subianto, who may challenge him again in 2019. So might the current chief army commander, Gen. Gatot Nurmantyo.

"Basically this (anti-communist revival) seems to me driven by (the) 2019 presidential election politics, in which the opposition to Jokowi is looking for anything they can find to discredit him," Liddle says.

Two recent polls suggest military officials may be missing the mark. One nationwide survey released in late September from Indikator Politik Indonesia showed Jokowi as handily the front-runner in the 2019 race. In an open-ended question where respondents could suggest any individual, 34 percent cited Widodo (over just 11 percent for Prabowo), and in a follow-up where several possible names were suggested, 47 percent chose Widodo, over 19 percent for Prabowo. A second poll , from the Saiful Mujani firm showed that only 13 percent of Indonesians believe the Communist Party, outlawed since 1966, is actually experiencing a revival.

The military will likely escalate its soft pressure on Jokowi until the election, says Muharam, of the international tribunal. As an example, he cited the fact that Jokowi made a show of watching an infamous Suharto-era propaganda film called "The Treachery of the September 30th Movement/ Indonesian Communist Party" at the Presidential Palace last month, right after the military general Gatot gave an off-the-cuff order for the military to hold screenings.

Anti-communism has long been a pretext to suppress human rights and freedom of expression, which is already on the decline in Indonesia due to the broad application of blasphemy , defamation and hate speech laws.

"The Legal Aid Institute protests show how the idea of 'anti-PKI' is a very good excuse to crush freedom of expression," says Andreas Harsono, an Indonesia researcher with Human Rights Watch.