Britain and the Prospect of War Within Five Years

By Matthew Parish, Associate Editor

Friday 12 June 2026

The resignation of Britain’s Defence Secretary, John Healey, over a dispute concerning military spending is more than a moment of Westminster drama. It is a reminder that, for the first time in decades, serious people in government are once again asking serious questions about war. Healey’s departure, accompanied by criticism that the government is failing adequately to prepare for a more dangerous world, has exposed a debate that extends far beyond budgets and procurement plans. The question is no longer whether the international security environment is deteriorating. The question is whether the United Kingdom herself might find herself involved in an armed conflict within the next five years.

For much of the post-Cold War era, Britain enjoyed the luxury of assuming that major interstate conflict was something that happened elsewhere. British forces participated in military operations in Iraq, Afghanistan, Libya and a range of peacekeeping and counterterrorism missions, but these were discretionary interventions rather than conflicts that directly threatened the British homeland or the survival of the state. The strategic assumptions underlying British defence policy were shaped by this reality. Armed forces became smaller, procurement programmes slower and public attention drifted elsewhere.

Russia’s invasion of Ukraine changed that. The war demonstrated that large-scale conventional warfare had not disappeared from Europe. It had merely been sleeping. Moreover the conflict exposed the degree to which modern warfare depends upon industrial capacity, technological innovation and societal resilience. Drones, electronic warfare, cyber operations and mass production of munitions have become decisive. The experience of Ukraine has forced defence planners across Europe to reconsider assumptions that had become almost articles of faith.

The irony is that Britain’s armed forces remain among the most capable in Europe while simultaneously suffering from profound structural weaknesses. The Royal Navy continues to possess globally deployable capabilities, including nuclear-powered submarines and aircraft carriers. The Royal Air Force remains technologically advanced. Britain’s nuclear deterrent continues to provide the ultimate guarantee against existential threats. Yet manpower shortages, procurement delays and budgetary constraints have left many questioning whether these strengths are sufficient. The very public disagreement that appears to have precipitated Healey’s resignation concerned precisely this issue: whether Britain is investing enough to meet the threats it faces.

Will Britain therefore be at war within five years?

The answer depends largely upon what one means by war.

If one imagines a replay of the Second World War, with enemy armies landing on British shores and mass mobilisation of the civilian population, the prospect remains remote. Britain’s membership of the North Atlantic Treaty Organization alliance, combined with its nuclear deterrent, makes a direct attack upon the United Kingdom extraordinarily unlikely. Any adversary contemplating such an act would face overwhelming risks.

However, modern conflict increasingly occupies the space between peace and total war. Cyber-attacks against infrastructure, sabotage, disinformation campaigns, attacks on undersea cables and covert operations have already become commonplace. In many respects Britain is already engaged in a form of low-level confrontation with hostile states. The distinction between peace and war is becoming progressively harder to define.

The most plausible route to British involvement in armed conflict lies through alliance commitments. If Russia were to expand military pressure against NATO’s eastern members, Britain would almost certainly be involved. British forces are already deployed across Eastern Europe as part of NATO deterrence arrangements. A crisis involving the Baltic states would immediately engage British strategic interests.

Yet Russia is not the only potential source of conflict. Escalating tensions in the Middle East continue to threaten shipping routes and energy supplies. The Indo-Pacific region is becoming increasingly contested. Britain’s commitments under arrangements such as AUKUS and its broader security relationships with allies mean that events far from Europe could draw British forces into military operations.

Nevertheless it is important to distinguish between possibility and probability. Public discourse often exaggerates the likelihood of imminent war. States generally seek to avoid direct conflict precisely because the costs are so high. Russia has suffered enormous losses in Ukraine. China understands the economic consequences of military confrontation. Even regional powers tend to calibrate their actions carefully.

The more immediate concern may be that Britain could enter a period of chronic strategic competition rather than formal war. Defence planners increasingly speak of an era in which societies must remain permanently prepared for confrontation. This does not necessarily mean continuous combat. It means living in a world where hostile cyber operations, economic coercion, espionage and proxy conflicts become normal features of international relations.

This is why the argument surrounding defence spending matters. The issue is not simply whether Britain can field a larger army or purchase more equipment. It is whether the British state can adapt quickly enough to a security environment changing faster than many political institutions are accustomed to managing. Critics of current policy argue that Britain is attempting to prepare for future conflicts using assumptions inherited from previous decades. Supporters of the government’s approach counter that resources are finite and that defence must compete with other priorities.

History suggests that wars often occur not because governments desire them but because they fail adequately to prepare for changing circumstances. The lesson of the twentieth century is not that conflict is inevitable. It is that complacency can be dangerous.

Will Britain be involved in an armed conflict within five years? The answer is that she may well be. The probability is considerably higher than it appeared ten years ago. Yet the form of that conflict is unlikely to resemble the wars that dominate popular imagination. It is more likely to involve a combination of cyber warfare, alliance obligations, technological competition and limited military engagements than a direct struggle for national survival.

John Healey’s resignation may ultimately be remembered not for its immediate political consequences but for what it revealed about Britain’s strategic anxieties. Behind the arguments over percentages of GDP and Treasury settlements lies a deeper recognition that the post-Cold War world has ended. Britain is entering a more dangerous age. Whether that age produces war will depend not only upon the intentions of Britain’s adversaries but also upon the seriousness with which Britain prepares for the challenges ahead.