Recent debates regarding the United Kingdom’s defence ambition have highlighted the important question of how to assess military capability. Here we propose 11 criteria for measuring military power.
The debate regarding the level of the United Kingdom’s defence and security ambition was recently given added political piquancy with the news that Prime Minister Theresa May had reportedly challenged the Ministry of Defence (MoD) to justify why the UK should remain a ‘tier one’ military power. This was subsequently denied by the prime minister, but not before the new Chief of the Defence Staff, General Sir Nick Carter, commented that all countries, in some way or another, think they are a tier one military power.

Although the discussion in the UK rapidly became part of debate on the direction of London’s Modernising Defence Programme (MDP) defence review, it serves to highlight the important question of how to assess military capability. The ideal for national governments in addressing their defence and security needs should be to agree an overall strategic assessment of the character and scale of the threats they face and seek to provide capabilities that can, as closely as possible, address these. However, the return of great-power, or state-on-state, competition, is leading to a renewed focus on how to assess relative military capability.

In deciding what military capabilities to procure, or simply to maintain in service, political leaders and military planners have to find solutions that bring into some sort of equilibrium threat analysis, available resources and the level of ambition a country defines for itself. The UK’s MDP is designed to this end, and UK allies will be engaged in similar processes.

In the UK context, tiers have been used before in the public-policy debate. For instance, in the 2015 Strategic Defence and Security Review (SDSR), they were used to define risks to the UK. The SDSR said: 'The NSC [National Security Council] places the domestic and overseas risks we face into three tiers, based on a judgement of the combination of both likelihood and impact. This is not, therefore, a simple ranking of their importance.’ But there is little currently available on what tiers mean in the context of UK MoD defence thinking.

This perhaps reflects that public debate about these matters tends to oscillate between two extremes. In one, countries may be grouped into some form of structure, like tiers, without much supporting explanation. Another approach is to analyse military capability through complex frameworks drawing together judgements including on doctrine, organisation, training, materiel, leadership and education, personnel, facilities and interoperability, known in NATO parlance as DOTMLPFI or, in UK terminology, Defence Lines of Development (DLODs – training, equipment, personnel, information, concepts and doctrine, organisation, infrastructure and logistics).

Assessing military power
The IISS has for some 60 years provided military data and analysis in The Military Balance and, more recently, the Military Balance+ electronic database, to help analysts assess military capability. While it began as a solely quantitative publication, The Military Balance has since explored more qualitative elements of military capabilities, such as flying hours and the legislative hurdles that states have to overcome before they can deploy their military forces. Indeed, for a rigorous ranking of military power, a large number of quantitative and qualitative variables need to be assessed. However, for a basic judgement on what kind of military actor a country is and aspires to be, it should suffice to examine its core capability portfolio.

Using a list of 11 criteria, we propose a distinction between global military powers, expeditionary powers and regional military powers. This proposal assumes that crucial differentiators in measuring military power are:

combat capability (war fighting in pursuit of national interests);
the potential to conduct operations across the spectrum of (and increasingly below) actual war fighting;
maintaining balanced combat, combat-support and combat-service-support capacity;
the range or distance at which operations can be conducted away from home territory;
the ability both to surge for rapid intervention and to support enduring operational requirements over extended periods of time.
We think this is a valuable building block relating to a state’s military potential. It is not necessarily hierarchical. And while some countries may maintain significant military holdings, levels of training and operational experience might influence a judgement of how globally significant their capability is. Indeed, it is important to remember that some countries may choose to limit the utility of their military power. Restrictions on expeditionary military power could be one example, based on national levels of ambition and factors including history and military culture. Japan is a good example of this: it has significant latent capability, but it chooses to deploy its armed forces abroad only in very constrained and limited circumstances.

Our approach also takes into account the fact that, as new elements of military power become significant, new thinking is becoming necessary to help analysts make judgements like those that have been made in the past about more traditional elements of military power. A notable case is cyber and also how states realise and integrate the promise of newly emerging militarily-relevant capabilities such as artificial intelligence and quantum computing.

These broad categories (global/expeditionary/regional) inevitably include within them distinctions concerning relative advantages in certain capability areas. For instance, the scale of capabilities, as well as their quality, will inevitably give certain countries relative advantages over others in the same category, particularly in the context of different military contingencies. Examples here include the UK’s advantage in strategic airlift compared to France, and the case in the initial stages of the war in Afghanistan when France was able to deploy a strike-carrier capability that was not – at that time – an option for the UK.

Capability matrix

Using the matrix above confirms that the United States currently is the only global military power. In particular, its conventional military capability is in a class of its own, with the ability to deploy and sustain global deployments and maintain combat missions on land, at sea and in the air. This is not, of course, to say that US deployments do not lead to significant stresses on the force, but Washington retains the ability to plan, deploy, sustain and fight at distance – and at scale – from the US homeland across the land, sea, air and space domains and in the electromagnetic spectrum in a way currently possible for no other nation.

The heading ‘expeditionary power’ refers to countries with a proven ability to deploy limited capabilities at strategic range. France and the UK fit into this category; each have relative strengths that would give them advantages in certain contingencies. China and Russia also fit into this category, with both countries possessing significant advantages in terms of their nuclear capabilities and the overall scale of their armed forces but not – for now, at least – in their ability to project large-scale conventional power at continental range for a sustained period. The issue for France and the UK in particular is whether and to what extent they may have to trade some traditional strengths in order to invest in new requirements.

Regional military powers, on the other hand, are focused on territorial defence and tasks within their immediate neighbourhood. While they might be very capable in that particular setting, in general they lack the capacity for global force projection. Examples would include not just Japan, already mentioned, but also Germany, India, Iran, Italy, the two Koreas, Pakistan and Saudi Arabia.

The key factor is that this is not a static but a dynamic matrix, set against a backdrop of significant strategic upheaval. The apparent trajectory of major players like China and the decisions that some states – like the UK – face could significantly affect their portfolio of capabilities and their standing as global, expeditionary or regional military powers.


Bastian Giegerich, Director of Defence and Military Analysis

Nick Childs, Senior Fellow for Naval Forces and Maritime Security

James Hackett, Editor, The Military Balance; Senior Fellow for Defence and Military Analysis