Communalism and terrorism despite having distinguishable definitions and have different contents shows similar pattern of regularity which can be termed as 'form.' In short, both take the form of violence of various natures as the consequence; unleashing fear and hatred in the minds of the people. Both are inter-linked to each other and cannot be seen as two set of different phenomenon independent of each other. This is particularly true in the Indian context today and is very much relevant.
What communalism, in common parlance, does is that religion (most commonly) or language, caste, ethnicity, etc. is used by its propagators as a means to achieve desired political goals. While terrorism is a phenomenon in which unjustifiable criminal acts are committed by terrorists to provoke a state of terror in the general public to achieve any targeted goal(s). Terrorism often uses the languages of religion, ethnicity, a particular ideology, etc. to justify terrorist acts in India. Thus, most of the religious fundamentalism based terrorist attacks in India has more or less finds its connection with communal-riots that often targets minorities. Hence terrorism seems to be an appropriate tool to retaliate against those communal mongers and seemingly supporters by those who had become the worst victims of communal-riots and communalism and yet hadn't given deserved justice.
What precedes what is a matter of debate, however, the circular reasoning that communalism and terrorism are inter-linked and goes in a cycle is a well-established fact that can be explained by relevant examples.
The 1992-1993 Mumbai (then Bombay) riots preceded the March 1993 terror attack. The BN Srikrishna Commission, appointed to inquire the riots, noted, "the blasts seem to be a reaction to 'the totality of events' at Ayodhya and in Mumbai in December 1992 and January 1993." The Commission also added that the then communal frenzy Shiv Sena leader, Bal Thackeray, and his party (Shiv Sena) played a pivotal role to charge up the Hindus by inciting communally charge propaganda against Muslims.
The Commission added that the subsequent Mumbai terror attacks was conspired mainly by the Muslims which is believed to be planned by international terrorist Dawood Ibrahim and his associates. According to official figures, 257 people (mostly Hindus) died in the terror attack; while 900 people (mostly Muslims) died in the riots.
On December 6, 1993, dozens of trains were bombed by suspected Indian Mujahideen jihadists, many of them had trained in Pakistan. The blasts marked the first anniversary of the infamous Babri Masjid demolition in Ayodhaya. Similarly, post-Godhra Gujarat showed a sharp increase in the recruitments of jihadists by invoking the killings, rapes and injustice done to Muslims and minorities. Thus every communal riots fuels terrorists groups to recruit more cadres. The recent controversial comment by the Congress Vice-President, Rahul Gandhi, on the ISI attempting to recruit the Muzaffarnagar riots victims is just the tip of an iceberg.
Other forms of communalism that are relevant in India are ethnic based communalism which are prevalent in the North-eastern states like Manipur and Nagaland where there have been cases of ethnic riots among major ethnic groups (Nagas and Kukis in Manipur) and resultant rise of terrorism as a retaliatory measure against each other; linguistic communalism of Shiv Sena and MNS in Maharashtra; and caste-based communalism which is relevant among mainly Hindus both in Northern and Southern India.
In this light, there is a link between communalism and terrorism. Communalism breeds terrorism and terrorism also gives incentives to communal-mongers to incite riots and pogroms at the same time in retaliation. The judicial system of India, particularly the Supreme Court, has acknowledged the link and given fair judgement in many cases. But our judicial system has limitations in delivering justice to victims. One main reason is its abysmally slow process. As for the Indian state, it should act against both the rioters and attackers equally to give a real sense of equality before the law. It must ensure that our education system imparts only liberal, secular and progressive education to all the citizens. As far as communalism is concerned, we must uphold the secular ethos that is enshrined in the Constitution in words and deeds. Diversity is a reality in India and we must appreciate the diversity and its beauty. If terrorism is to be uprooted, we must be clear of one thing- bridging the gap of trust and harmony between various communities and prevent, if any, fracture of Indian society based on communal lines.