For years, the language of “infiltration” had been one of the Bharatiya Janata Party’s (BJP’s) most reliable electoral weapons in eastern India. This deliberately elastic phrase has fused anxieties about borders, demography, security and Islam into a single political factor. In West Bengal, where history itself is partitioned by migration and displacement, the rhetoric carried unusual force. Yet even by those standards, the party’s campaign this time was strikingly blunt. BJP leaders repeatedly promised to identify “illegal Bangladeshi migrants,” strip them of protections and, in some cases, send them “back” across the border. During past elections, Dhaka had learnt to treat such threats as campaign-season theatre. This time it is treating them as strategic intent.That shift explains why, within days of the BJP’s sweeping victory in West Bengal, Bangladesh’s border forces quietly moved to tighten patrols along sections of the frontier near Benapole in Jashore. Officials in Dhaka framed the move in procedural terms as vigilance against any illegal “push-ins” by India’s Border Security Force. But the underlying message was political. Bangladesh believes that migration has moved from being a domestic talking point in India to becoming an organising principle of bilateral relations.The symbolism matters. West Bengal shares more than 2,200 kilometres of border with Bangladesh, the longest India shares with any neighbour. New Delhi’s relationship with Dhaka, in most part of the past few decades, rested on a careful bargain. India would publicly celebrate Bangladesh as a strategic partner while privately complaining about undocumented migration. Bangladesh, meanwhile, would reject the accusation while cooperating selectively on security matters. Both sides understood the fiction. Neither side pushed it too far.Now the fiction is fraying.The BJP’s triumph in Bengal alters the political geometry of the border. The party’s claims about “Bangladeshi Muslim infiltrators” were historically constrained by the fact that West Bengal itself was governed by the Trinamool Congress, which viewed such rhetoric as politically toxic and economically destabilising. The state government resisted efforts to operationalise aggressive citizenship drives or deportation campaigns. That barrier has disappeared. For the first time, the BJP controls the politics of the frontier as well as the narrative around it.The result is likely to be a harder, more securitised bilateral relationship in which migration ceases to be a secondary irritant and becomes the central framework through which India views Bangladesh. Also read: The Assembly Poll Results Take Us Back to the 1967 Moment: Not the End but the Beginning of the Real FightNew Delhi’s response to Dhaka’s protests after the election already suggested as much. Rather than downplaying the issue, India’s external affairs ministry publicly urged Bangladesh to accelerate the repatriation of “illegal Bangladeshi immigrants”, effectively elevating the matter from campaign rhetoric to diplomatic agenda.That is a significant shift. Historically, India’s external affairs establishment preferred to treat migration as an internal administrative matter, partly because publicly internationalising it risked antagonising a government in Dhaka that had otherwise been among India’s most cooperative regional partners. Ousted autocrat Sheikh Hasina’s administration cracked down on anti-India insurgents, deepened security coordination and granted India transit and connectivity concessions that previous Bangladeshi governments had resisted. In return, India generally avoided public humiliation.But the politics of Hindu nationalism increasingly rewards confrontation over subtlety. The BJP’s rise has turned the border itself into an ideological object: proof of sovereignty and civilisational control. Within that worldview, undocumented migration is not merely an economic or administrative concern. It is presented as demographic encroachment by Bengali-speaking Muslims into India’s east. That framing leaves little room for diplomatic ambiguity.Bangladesh faces a difficult asymmetry. Economically and strategically, it cannot afford a prolonged rupture with India. Yet politically, no Bangladeshi government can publicly accept India’s characterisation of large-scale “Bangladeshi infiltration” without appearing to surrender national dignity. Dhaka therefore finds itself trapped between dependence and defiance.That imbalance is sharpened by the changing nature of diplomatic representation between the two countries. India has increasingly abandoned the old model of treating Bangladesh as a secondary bureaucratic posting. Instead, New Delhi has deployed a political heavyweight in Dinesh Trivedi, a veteran parliamentarian with deep networks across India’s ruling establishment and a direct understanding of Bengal’s volatile political culture. Trivedi’s importance lies less in diplomacy than in access. He can navigate power centres in Delhi, communicate directly with political leadership and shape narratives inside the BJP ecosystem itself.Bangladesh, by contrast, continues to rely on the traditional machinery of career diplomacy. Its envoy, M Riaz Hamidullah, is an experienced diplomat but not a political operator with influence comparable to Trivedi’s. The distinction matters because India-Bangladesh relations are no longer driven primarily by technocratic consensus or bureaucratic management. They are increasingly shaped by domestic political narratives inside India, particularly those linked to migration, citizenship and Hindu nationalism. In such an environment, access to political power matters more than procedural expertise.Hamidullah’s difficulties during the Yunus-led interim government underscored that limitation. As bilateral tensions rose and Indian political discourse hardened, Dhaka struggled to maintain strategic clarity with New Delhi. Communication became reactive rather than influential. Bangladesh often appeared to be responding to developments in India rather than shaping them. The absence of a politically connected envoy capable of reading and managing the BJP’s internal dynamics became increasingly evident.That imbalance may now become structural. The BJP’s Bengal victory effectively domesticates Bangladesh within India’s electoral politics. Every incident along the border—whether migration or communal tension – now carries direct political value for the ruling Bangladesh Nationalist Party (BNP). The temptation to periodically escalate the issue will remain strong, particularly if the BJP seeks to consolidate Hindu votes through a politics of demographic anxiety.Also read: Breaking: Suvendu Adhikari, Who Said He ‘Will Work for Hindus’, Named Bengal CM by BJPFor Bangladesh, the danger is not necessarily mass deportation; logistical and legal constraints make that unlikely on a large scale. The greater risk is a steady normalisation of coercive border practices that include sporadic push-ins, heightened verification drives, arbitrary detentions and a permanent rhetoric of suspicion directed at Bengali-speaking Muslims near the frontier. Such measures may not fundamentally alter migration patterns, but they can steadily poison political trust.There is also a deeper irony. India’s obsession with “illegal Bangladeshi migrants” persists even as Bangladesh’s economic trajectory has changed dramatically over the past two decades. Bangladesh is no longer the impoverished basket case of Indian political imagination. On several social indicators, from life expectancy to female workforce participation, it has outperformed India. Migration flows today are more complex than the simplistic image invoked in Indian campaign speeches. Yet politics rarely rewards nuance.The problem for both countries is that migration rhetoric, once unleashed, acquires its own momentum. The BJP cannot easily retreat from a narrative that helped deliver one of its most consequential victories in eastern India. Bangladesh, meanwhile, cannot publicly acquiesce to being cast as the source of India’s demographic anxieties. The result is likely to be a relationship increasingly defined not by the strategic optimism that characterised the Hasina years, but by mistrust concentrated around the border itself.South Asia’s frontiers have always been political theatres as much as geographical lines. In Bengal, where partition never fully ended and identity still flows uneasily across borders, that theatre is becoming more combustible. The thing that once sounded like campaign rhetoric is beginning to look like policy language. Dhaka has noticed. And this time, it is not assuming the shouting will stop once the votes are counted.Faisal Mahmud is a Dhaka-based journalist.