An Empire’s Shadow War: How the IRA mastered asymmetry in Britain’s backyard

Our series on asymmetric warfare revisits pivotal moments in modern history when underdogs rewrote the rules of war, and forced superpowers to reckon with new realities.

PART - 4

Across a century, from Michael Collins’s urban assassins to Gerry Adams’s ballot-box revolutionaries, the IRA forced Britain to fight a war it never fully understood, while forcing it to confront the limits of force and legitimacy.

In the latter half of the 20th century, Britain found itself locked in a guerrilla conflict unlike any it had faced in decades. The Provisional Irish Republican Army (IRA), rooted in the earlier IRA of Michael Collins, waged a protracted campaign across urban streets, rural lanes and political halls. In doing so, it forever reshaping the laws of guerrilla warfare.

The blueprint for urban insurgency was drafted in 1920. Under Michael Collins’s direction, the IRA’s intelligence unit (later dubbed The Squad or the ‘Twelve Apostles’) executed targeted assassinations of British intelligence agents on Bloody Sunday, November 21, 1920.  These meticulously planned killings of Cairo Gang operatives shattered British command structures and erected a psychological barrier in which no agent was safe.

Collins’s strategy hinged on deep human intelligence, surprise and urban ambush. Journalist and historian Tim Pat Coogan, the author of standard works on Collins and the IRA, observed how Collins wove danger into the urban fabric of Dublin, transforming his city into a lethal web.

New Doctrine

By the late 1960s, the Provisional IRA emerged from Northern Ireland’s civil unrest with a new doctrine, captured in its secretive ‘Green Book’ which codified its tactics of a war of attrition against British forces, relentless bombing campaigns and the goal of engineered ungovernability. Urban environments were both battleground and theatre. The IRA placed bombs in city centres, deployed sniper teams in Belfast, and used ‘come-on’ tactics to lure British patrols into ambushes. Their aim was not just body counts, but psychological dominance to show Britain that Northern Ireland could not be governed without Irish consent.

Tim Pat Coogan highlights how this tailored insurgency drew deeply from Collins’s early lessons and were now adapted for modern urban conflict and mass media.

The Warrenpoint ambush of a British convoy in 1979 - where two bombs killed 18 British soldiers in the deadliest single attack of the conflict - showcased the IRA’s rural operational expertise. Here, in the borderlands of Northern Ireland, insurgents used elevated ambush positions and precise coordination in a rural parallel to Collins’s urban coups. The attack bookended the assassination of Lord Mountbatten on the same day in a symbolic decapitation of Britain’s aristocratic war hero.

Simultaneously in cities like Belfast and Derry, the IRA’s Active Service Units (ASUs) launched sniper attacks, mortar strikes and bombs. Bloody Sunday in 1972 intensified their cause when firing by British soldiers on civil rights demonstrators in Derry propelled thousands toward the IRA’s ranks.

Tactical Ruthlessness

The most chilling phase of the IRA’s tactical development came in the early 1990s with the use of ‘proxy bombs’ by which they coerced civilians to act as unwilling suicide bombers. In one instance in 1990, a young man, Patrick Gillespie, was strapped into a van full of explosives and ordered to drive into a British checkpoint. It detonated, killing him and five soldiers. The reaction was immediate - public revulsion, international condemnation and even internal unease. Yet, the political message behind these tactics was to show that even total surveillance and high-tech fortresses could be breached with one terrified man.

By the late 1980s, the Sinn Féin under Gerry Adams had begun to chart a new course. The strategy of ‘the Armalite and the ballot box’ proposed that armed struggle and political negotiation could operate in tandem. Elections became not a surrender to constitutionalism, but a tactical extension of war.

This dual track placed Britain in a dilemma. Military escalation risked radicalising nationalist communities, but political compromise risked legitimising what it continued to call ‘terrorism.’ Adams, a man who “never held a gun but never disowned those who did,” was a master of calibrated ambiguity. Sinn Féin’s electoral surge, particularly in working-class nationalist areas, finally began to achieve what bombs could not - a seat at the table.

Throughout the struggle, the British state, for all its might, struggled to adapt. Its tactics like mass internment without trial in 1971, or the use of informants and the infamous ‘supergrass’ trials, often backfired as repression bred resistance and the heavy hand of British intelligence often fuelled IRA recruitment.

Under Adams’s leadership, Sinn Féin embraced electoral politics while continuing IRA operations. This dual strategy culminated in the 1994 ceasefire, embedding violence within a political framework and empowering Adams as the movement’s spokesperson and negotiator. The cessation of violence with the 1998 Good Friday Agreement marked a watershed moment. Yet, Gerry Adams remained a polarising figure, hailed for tactical prudence but accused by many others of privately keeping the IRA’s armed wing alive for leverage.

The IRA’s century-long war - from Collins’s Dublin hit-squads to Adams’s parliamentary presence - shaped a modern insurgent lexicon. Its blend of assassination, political messaging, rural ambush and urban terror offered a template for modern non-state warfare. This doctrine influenced the Basque ETA’s campaign in Spain, Latin America’s guerrilla movements and even militant wings in South Asia. It demonstrated that asymmetry was not a tactical convenience but a strategic choice, capable of outlasting empires and outwitting armies.

During the 1970s and 1980s, insurgent groups in Spain’s ETA and Colombia’s FARC studied IRA methods, particularly in intelligence operations and urban bombings. Palestinian groups also adapted aspects of IRA urban guerrilla theatre, combining attacks with media-savvy messaging. The IRA’s model showed that small, determined units could inflict outsized political impact, provided they mastered local terrain, built popular networks and sustained media attention.

In Nicaragua’s Contra war and later in El Salvador, guerrilla movements drew on IRA-style shock-and-awe ambush tactics against better-equipped governments. The concept of asymmetrical attrition - hitting hard enough to erode public support for an occupier or central authority - became ubiquitous. The IRA’s success in urban theatre validated insurgent doctrine around the world. In El Salvador, the Farabundo Martí National Liberation Front (FMLN) employed hit-and-run operations in San Salvador not unlike IRA Active Service Units in Belfast, using civilian cover, political messaging, and decentralised command. In Nicaragua, while the Contras drew inspiration more from U.S. Cold War sponsorship, their use of cross-border safe havens, psychological warfare, and attacks on infrastructure bore echoes of IRA strategies.

In South Africa, the African National Congress’s armed wing, Umkhonto we Sizwe (MK), was acutely aware of the IRA’s war against a liberal democratic state. While MK operated under different circumstances, it found in the IRA a model for how to combine international sympathy, sporadic violence and underground cells with a political party.

The Tamil Tigers in Sri Lanka, too, mirrored the IRA in their dual-track strategy of terror and governance, often citing Northern Ireland as a case study. Their suicide bombings, assassination of public figures and creation of a shadow state bore resemblance to the paramilitary and political duality the IRA had perfected.

Thus, the IRA, initially dismissed as a relic of imperial detritus, became a reference point for revolutionaries from Medellín to Mitrovica. It was not merely their methods but their endurance that inspired. The IRA showed how a movement could survive for decades, fragment and recombine and extract political concessions from a far stronger adversary without ever formally surrendering.

(In the final part of this series tomorrow, we journey through the blood-soaked alleyways of Algiers, the safehouses of Bilbao and the jungles of Jaffna to examine how the FLN, ETA and the LTTE each redefined insurgency and asymmetric warfare for their time)