Britain faces a closing window to prepare its armed forces for a potential conflict with Russia and must begin mass mobilisation immediately, according to a new report from the Royal United Services Institute that delivers a stark warning to a government accused of chronic indecision on defence.
The report, authored by RUSI Senior Associate Fellow Paul O’Neill, argues that the country’s land forces will need to double in size to meet the threat posed by Russia, and that the systems currently in place to recruit, train and absorb new personnel are wholly inadequate for what may lie ahead. O’Neill told The Sun that the ideal moment to have begun scaling up mobilisation planning was “ten years ago,” adding bluntly: “The next best time is now.”
The scale of the challenge is considerable. Britain’s regular army currently stands at around 73,790 soldiers — less than half the 153,000 it fielded at the end of the Cold War, after decades of underfunding and cuts. Volunteer reserve forces add a further 31,900 personnel, representing 17.5 per cent of total armed forces strength. A theoretical strategic reserve of 90,000 exists on paper, but the report dismisses that figure as unrealistic in a genuine conflict scenario due to significant overlaps in specialist skills and the limitations of the single-centre system used to call up and train personnel, which O’Neill warned would quickly become overwhelmed under pressure.
The RUSI report is clear that what is needed goes well beyond simply expanding the volunteer reserves or recalling former service personnel. It calls for a whole-of-society approach that draws on the full range of national talent and industry, preparing not just military forces but the broader economy and manufacturing base for the possibility of sustained conflict. “Policymakers and the public should be disabused of the idea that the UK armed forces do not need to field a large force to match a potential adversary,” the report states, warning equally against leaving detailed planning until a crisis actually arrives.
On the question of conscription — for decades considered politically toxic in Britain — the report is nuanced. It stops short of recommending full compulsory service, noting that society is not ready for it and that the armed forces currently lack the capacity to absorb and meaningfully train a large conscript intake. Instead, it points to France as a model, suggesting a small-scale selective programme as a way of testing the concept and identifying the practical challenges that broader conscription would entail.
O’Neill acknowledged the political difficulty of asking governments to commit to the economic costs of mobilisation before a conflict feels inevitable, but said the UK’s historical habit of acting too late — in both the First and Second World Wars — could not be repeated. “Is it going to be too late? I don’t know,” he said. “We have a tradition in the UK of doing these things too late. But I think we need to start the growth journey now.”
Among the report’s other recommendations are the development of a formal blueprint for wartime mobilisation with clearer defined roles for reservists and veterans, and a study of Ukraine’s experience to avoid the chaos of zero-notice emergency call-ups. The message throughout is consistent: the window for orderly action is narrowing, and the time to act is before the sirens sound, not after.
