How did a visit to Israel by a senior Islamic figure lead to members of Indonesia’s largest Islamic organisation, Nahdlatul Ulama (NU), accusing the nation’s second largest Islamic party, the Prosperous Justice Party (PKS), of behaving like communists who are out to destroy Indonesia? This is a tale about the fevered state of Islamic discourse in Indonesia, one nurtured in the hothouse of social media. It has been fuelled by long-standing and deepening doctrinal animosities as well as competing political interests. Its resonance will be felt in next year’s legislative and presidential elections.

The saga began in early June, when Yahya Cholil Staquf, the secretary of NU’s Religious Council (PB Syuriah) and a member of President Joko “Jokowi” Widodo’s Advisory Council (Wantimpres) visited Israel. He travelled at the invitation of the advocacy group the American Jewish Committee (AJC) and gave a series of public lectures as well as met political and religious leaders and academics.

Yahya claimed he went to Israel out of concern for the Palestinians and a desire to foster peace in the Middle East. He also invoked the name of Abdurrahman Wahid (“Gus Dur”), Indonesia’s fourth president and former NU chair, who visited Israel on numerous occasions and served on the advisory board of the Peres Centre for Peace. Yahya ignored advice from many of his NU colleagues not to go and travelled without the approval of the NU Central Board.

News of the visit broke in the Islamic media on 9 June, sparking immediate controversy. When, a few days later, the Israeli press carried pictures of Yahya shaking hands with Prime Minister Benjamin Netanyahu, Islamist groups reacted angrily, calling on NU and President Widodo to censure or dismiss him for undercutting Indonesia’s long-standing pro-Palestinian policy and for playing into the hands of an Israeli government that had only recently shot dead more than 50 Palestinians on the Gaza border. Criticism of Yahya sharpened when it was reported that he failed to meet any Palestinian leaders and had been “severely censured” by Hamas in a press statement on 11 June.

Some of the most trenchant commentary on Yahya’s visit came from PKS. Party elder Hidayat Nur Wahid scoffed at the suggestion that the visit helped Palestinians, stating that the AJC had “twisted [Yahya’s] visit to Israel’s advantage, not for Palestine’s”. Former PKS president Tifatul Sembiring remarked, presumably sarcastically, that he’d “only just become aware that Yahya was an Islamic scholar (kiai)”. Most inflammatory of all was the North Sumatran PKS leader, Salman Alfarisi, who tweeted: “Not content with being on the Wantimpres … this cockroach (cecunguk) carefully seeks fame in Israel. Does he want a second job on the Israeli Wantimpres?”

Officially, NU’s response to the controversy was measured. Its leaders assured the media that NU’s support for the Palestinian cause was unwavering and that Yahya’s visit was a personal initiative. Some of the more progressive leaders defended Yahya, pointing to his long record of interfaith activism and his efforts to promote moderate and tolerant Islam globally. In private, though, many on the Central Board were displeased by the visit, believing it achieved little and showed Yahya’s inflated sense of his own international stature.

But it was the PKS criticism and denigration of Yahya that most aroused ire in NU’s ranks. NU social media lit up with denunciations and ridicule of PKS. Younger, media-savvy NU activists mounted counter-attacks against the party on Twitter, using hashtags like #tenggelamkanPKS (#sinkPKS) and #guremkanPKS (#belittlePKS). Most featured mocking or castigating images and comments. For example, one showed a rubbish truck carrying crates with tattered PKS signs, and others had memes depicting a submerging PKS ship with the gloating tagline “PKS sinks in Java”, following the party’s supposedly poor June regional election results. (Most political observers believed that PKS had actually performed above expectations in the elections.) Another widely shared meme bore the words: “Thank God I am not PKS”.

But it was the NU-linked Duta.Islam site that pressed the attack furthest. In a series of articles published in late June, various writers vilified PKS for a succession of perceived evils. One article accused the party of being part of a Saudi Arabian plot to take over Indonesia. It declared: “PKS’s main agenda is to destroy Indonesian culture via the invasion of Saudi Arabian culture”, calling the party an “extension of the hand of the Saudi Kingdom”. It claimed the Saudis planned to take over Indonesia’s resource wealth because their own oil reserves would be exhausted in 30 years, and the “most direct way of doing this was by cultural invasion”. It concluded that once traditional Islamic culture was deemed “polytheistic and deviant”, then the “Unitary Republic of Indonesia would be destroyed”. This trope drew on a common view in NU that all “transnational” Islamist groups, such as PKS and Hizbut Tahrir, are Wahhabist/Salafist – a categorisation few independent scholars would agree with.

Duta also cast PKS as a national threat due to the party’s supposed links to Darul Islam and other “treasonous” movements. Darul Islam declared Indonesia to be an Islamic state in 1949 and waged armed rebellion against the Republic in the 1950s and early 1960s. Among the PKS leaders mentioned as being from Darul Islam families was Hilmi Aminuddin, one of party’s most revered Islamic scholars and founders, who was the son of a senior Darul Islam commander. Other articles referred to PKS leaders supporting the now-banned Hizbut Tahrir, or of having pro-ISIL sympathies.

Most extreme of all, the website likened PKS to the Indonesian Communist Party (PKI), which has been banned since 1966. In an article titled “PKS is PKI in Religious Garb”, the unnamed author listed 15 similarities between the two, including that both were cell-based, cadre parties that demanded uncritical study of key texts (Karl Marx for the PKI, Hasan al-Banna for PKS), as well as full compliance with party leaders’ instructions. To drive the point home, an accompanying meme altered the PKS symbol of two crescent moons and a sheaf of wheat to show two sickles and a hammer. Another image implied that PKS was “neo-PKI”.

Such public NU broadsides against PKS are without precedent. Mutual suspicion and tensions between the two organisations have existed since the party was founded in the late 1990s, but rarely have NU-affiliated media been so brazen in their attacks.

The reasons for this escalation go far beyond Yahya’s Israel visit. In recent years there has been growing concern in many sections of NU that it is losing the information war with Islamist organisations, and especially PKS, which has one the most social media-adept communities in Indonesia. During the 2014 Presidential Election, PKS members played a leading role in the “black campaign” against Widodo, who was favoured by a majority of NU members, spreading rumours that he was a closet non-Muslim and of Chinese descent. The party also featured prominently in virulent social media campaigns against Chinese Christian former Jakarta Governor Basuki “Ahok” Tjahaja Purnama. Many NU activists bear a particular grudge against the PKS-linked website Piyungan, accusing it of running aggressive, conspiracy-laden sectarian attacks on PKS’ rivals, including NU.

As a result, many younger NU members now see fightback as imperative, lest NU increasingly cede ground to its doctrinal and political opponents. NU’s championing of Islam Nusantara (Archipelagic Islam, as opposed to putative Arabised Islam from the Middle East) has been one part of this. The “Cyber Army” of NU youth wing Ansor is another. But the Twitter and web campaigns against PKS in the past month show NU’s determination to turn PKS’s own techniques against the party. The use of highly emotive and provocative language and images, as well as the resort to outlandish, maligning conspiracies, have been trademarks of the most notorious PKS-linked sites. Now NU, which likes to portray itself as a bastion of Islamic moderation, is immersed in unedifying discourses.

Of course, NU leaders will deny, with some plausibility, direct responsibility for the anti-PKS discourse, much as PKS leaders did with Piyungan, but they will hope to benefit from the pillorying of their foes. In the run-up to the 2019 elections, this ramping up of polarising, vituperative campaigning between two major Islamic communities augurs badly for the civility of Indonesian democracy.