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RUSI Hosts Allied Rapid Reaction Corps Study Day 2025: Refining NATO’s Cutting Edge

On 28 May 2025, theInternationally recognised London’s Royal United Services Institute (RUSI) once again opened its doors to welcome senior commanders, scholars and practitioners from across the Alliance for the Allied Rapid Reaction Corps (ARRC) Study Day 2025. Under the banner “How the 21st-Century Corps Fights,” the gathering examined how NATO’s Corps-level formations must evolve to meet the twin pressures of great-power competition and rapid technological change.

Commander ARRC Lieutenant General Ralph Wooddisse KCB CBE MC addresses the RUSI Corps study day 2025.

Founded in 1831 by the Duke of Wellington, RUSI is the world’s oldest independent think tank on defence and security. With a legacy rooted in the study of military science, it has long served as a trusted forum for intellectual exchange between government, military and academic leaders. Over nearly two centuries, it has hosted everyone from war-time prime ministers to NATO commanders, always with the aim of sharpening strategic thought and advancing practical understanding of conflict and security

Lieutenant General Christopher Donahue, Commanding General XVIII (U.S) Airborne Corps.

Chief of the General Staff Sir Roly Walker (British Army).

The programme opened with three keynote addresses that framed the day’s discussion. General Sir Roly Walker, Chief of the General Staff, offered a British perspective on delivering combat mass at speed, stressing that “credible deterrence rests on forces able to scale, integrate and endure.” He was followed by Lieutenant General Christopher Donahue, Commanding General XVIII (U.S.) Airborne Corps, who drew lessons from recent large-scale exercises on the eastern flank and underscored the indispensability of “allied readiness measured in hours, not days.” Lieutenant General Sir Ralph Wooddisse, Commander ARRC, closed the opening session with a candid appraisal of the Corps’ progress since taking on the role of NATO Strategic Reserve Corps (SRC) and outlined the path to full operational capability.

Panels delved into three core themes. “How Russia Fights” dissected Moscow’s evolving concept of layered fires and the importance of electronic warfare in blunting Western precision. “The Corps Level of Warfare: An XVIII Corps Perspective” highlighted American efforts to knit together joint-fires networks across multiple domains. Finally, “Protecting and Sustaining the Corps” scrutinised the logistics of fighting at scale while remaining survivable beneath the reach of long-range sensors and precision strike.

Throughout, RUSI moderators kept debate brisk, inviting probing questions on readiness, sustainment, lethality and survivability. A recurring topic was the “Corps trinity” of scale, complexity and endurance: the requirement to manoeuvre divisions, integrate joint and multinational enablers, and persist under contested conditions. Several speakers noted that the forthcoming Ministry of Defence Strategic Defence Review’s “NATO First” principle makes the ARRC’s success a litmus test for Britain’s broader defence policy.

By day’s end, one conclusion was clear: delivering a fully-fledged SRC is a national endeavour of formidable scale, but it is also the lynchpin of NATO’s future war-fighting concept. As attendees filtered onto Whitehall’s pavements, the mood was equal parts sober and energised—sober at the magnitude of the task, yet energised by the clarity of purpose that only frank professional dialogue can provide. Eight decades after Allied armies first advanced across Europe, the ARRC Study Day 2025 served as a timely reminder that Corps-level excellence remains the sharpest point of NATO’s spear.

Chief of the General Staff General Sir Roly Walker addresses the conference.