With over $40 billion worth of weapons and other assistance having been donated to Ukraine by Western nations since the start of the conflict last year, there is a distinct proxy war being waged by NATO against Russia. Ukraine is now a de facto member of the alliance, but Jens Stoltenberg has gone out of his way to avoid actions that could escalate the situation. Therefore, a devilishly simple question arises: how do we distinguish between proxy relationships and alliance relationships?

Any distinction at all is hard to make given how the latest shift in alliance war-waging by the West and its allies is a move away from conventional warfare – prompted by an aversion to ‘boots-on-the-ground’ conflicts of the War on Terror era – and towards a clear preference for achieving strategic interests indirectly through the provision of massive amounts of weapons and financial resource to preferred proxies instead. Alliance warfare is now increasingly war by proxy. Regional or global powers now often prefer to provide weapons informally to allied states in place of a formal defence pact, as it allows them to ‘signal reassurance while avoiding entrapment’. The Western response to the Russian invasion of Ukraine has become emblematic of this new shift.

Most scholarly work on alliance theory has been the product of those in the (neo)realist stable who have produced explanations of why states ally themselves, ranging from the need to maintain a balance of power (classical realists) to maintaining a balance of threat (neo-realists). The growth of the field has covered many areas, yet a distinct gap still exists – namely the issue of alliance behaviour during particular types of conflict. Understanding the implications of this is crucial if the informal supply of weapons to Ukraine by formal alliances such as NATO is to become the norm in how alliances conduct wars by proxy.

Proxy warfare in Ukraine

At the outset of the Russian invasion in February 2022, the Ukrainian military was equipped largely with Soviet-era artillery, aircraft and tanks. Within a few months, Western allies had transferred more sophisticated weaponry. A turning point occurred in June 2022, when the first High Mobility Artillery Rocket System (HIMARS) vehicles arrived, providing the Ukrainians with medium-range offensive launch capabilities for the first time. This was followed later that summer by the provision of self-propelled and wheeled artillery and armoured vehicles. As the war approached its first anniversary the West began to provide advanced support by acceding to long-standing Ukrainian requests for tanks. Britain pledged to send fourteen of its Challenger 2 tanks, while the US has so far committed thirty-one Abrams tanks. So great was the influx that, by the end of 2022, Ukraine had become the world’s third-largest weapons importer.

Around fifty countries have provided assistance to Ukraine, with the US being by far the largest donor. From the beginning of the war to July 2023, the US government has provided around $43 billion in security assistance to Kyiv, including over 2,000 Stinger anti-aircraft systems, over 10,000 Javelin anti-armour systems, twenty Mi-17 helicopters, and nearly two million rounds of 25mm ammunition. This quantity of arms and weaponry is clearly enough to challenge the Russian military occupation, but is insufficient to help the Ukrainian military retake large swathes of territory, as the 2023 summer ‘counter-offensive’ showed. This leaves the proxy war looking like it is motivated by a ‘bleed Russia dry’ strategic objective, which means maintaining Ukrainian military capabilities long enough to degrade Russian forces significantly in a war of attrition that Moscow had neither planned for nor had the means of maintaining without severe financial and political cost.

Despite some opposition to these weapons transfers on Capitol Hill and some indication from those in the Biden administration that more should be done, it is clear that the West has no good options: a proxy war carries risks, but short of courting all-out war with Russia it is the only viable option to prevent total Russian victory. A NATO-led proxy war cannot offer a single knockout blow to the Russian military, but it can facilitate death by a thousand cuts.

What do proxy wars tell us about alliances?

Glenn Snyder lamented in the early 1990s that alliance theory was ‘one of the most underdeveloped areas’ of international relations. Progress has been made since then, but there remains much to be done in terms of plugging the theory into other facets of international conflict, including proxy war, in order to extend explanations about behaviour in the international system. The issue of pre-existing alliances between eventual ‘principals’ (e.g. states who send arms) and ‘agents’ (e.g. the groups on the ground receiving the assistance) can play a large role in explaining proxy wars. If alliance reliability affects whether nations decide to go to war in a conventional inter-state conflict, then there is no reason to assume that the level of support from allies does not also impact the decision to intervene indirectly in a conflict. Complex conflict dynamics, or the desire to avoid sparking international opprobrium, may provoke certain alliances to manifest their solidarity in a proxy manner. If a nation is more likely to retaliate if provoked when it expects the support of its allies, then we must consider that the fulfilment of collective security pacts and alliance treaties can be achieved both through direct third-party intervention and by indirect proxy involvement.

Proxy wars are increasingly being waged multilaterally, almost to the point we can consider it as coalition proxy warfare. That is not to say that single-state proxy strategies are obsolete – they will of course continue – but merely that there has been a trend towards collective proxy strategies. The Western response to the 9/11 attacks cemented the trend for utilising ad hoc coalitions for military action over permanent alliances, which had been evident since the end of the Cold War. This has taken the form of either deliberate proxy coalitions, such as the efforts of the Global Coalition to Defeat Daesh, which saw the West work ‘by, with and through’ local partners in the war against Islamic State, or informal alliances that stem from mutual selection of the same proxy, such as that which united Syria and Iran through their support for Hizbollah in its battle against Israel.

There is thus a knock-on effect in understanding how alliance politics are perceived within contemporary international relations. The decision by groups of states to intervene by proxy in an existing conflict reveals not only a shared interest in the outcome of that war, but also demonstrates how collective security – through the removal of a mutually despised regime, for example – is not necessarily manifest through formal treaties, but is rather something more informally undertaken by the aiding and assisting of allies from a distance. Joint missile shields or collective security clauses in alliance pacts can now be joined by coalition proxy war-fighting as a manifestation of collective security in action in the twenty-first century. The Western reaction to the invasion of Ukraine is a testament to this.

One of the defining features of the literature on alliances is disagreement as to whether they must be formal or informal. While some scholars, such as Glenn Snyder and Alexander Lanoszka, have stressed the formal nature of alliances, as manifest through the presence of a written treaty, others such as Hans Morgenthau have erred towards an informal understanding of alliances (the formation of which he called ‘a matter not of principle but of expediency’). A middle ground has been forged by the likes of Stephen Walt, Michael Barnett and Jack Levy, who all define alliances as being ‘a formal or informal’ arrangement. The shift towards alliance warfare being conducted increasingly by proxy reinforces the more informal approach adopted by the likes of Morgenthau, not just because of the expediency involved in the calculations to diminish Russian capabilities at arms-length, but because, as Walt has argued, ‘the presence of a formal agreement often says relatively little about the actual degree of commitment’.

The future of the western proxy war in Ukraine

Understanding the reasons why some alliances endure or collapse is a crucial component of understanding collective behaviour in the international system. When thinking about how long the West’s provision of security assistance to Ukraine can continue it is worth returning to Stephen Walt’s twenty-five-year-old checklist of reasons why alliances fail. First, changing perceptions of threat emanating from Moscow could cause a split, especially if a desire to appease Putin by finding him an ‘off-ramp’ finds traction in European capitals. Second, the declining credibility of the alliance caused by the lack of tangible security gains could cause a deterioration. Lack of territorial gain by the Ukrainian military, combined with long-term, high-cost resource commitment by the West, could cause ructions (as demonstrated by the recent exasperated comments of the UK Defence Secretary Ben Wallace about how Ukraine needed to show more ‘gratitude’ and should stop treating NATO ‘like Amazon’ for weapons provision). Third, domestic politics can play a large role in defining foreign relations. The potential return of a second Trump administration to the White House in the 2024 US presidential election could usher in a new era of NATO division and a more sympathetic line towards the Kremlin. It should also not be discounted that Zelenskyy could be voted out of office or replaced within his party, creating a new set of leadership relations to be developed within Kyiv.

There is a danger that a rot can start to set in if NATO members start to perceive Ukraine as both resource-deficient and politically unimportant. Alliance politics is, as Barbara Elias reminds us, ‘an interactive bargaining process’. The asymmetry of the relationship between Ukraine alone being asked to shoulder the burden of repelling Russian forces from their territory and NATO member states providing the vast majority of the weapons and finance to help achieve this leaves this informal alliance particularly vulnerable. The lack of a clear strategic endgame for the West’s proxy war also doesn’t help (is it a return to 2014 borders or the liberation of Crimea, too?). However, as Edwin Fedder wrote in the late 1960s, all alliances are ‘manifestations of organised international cooperation… that are restricted to specified goals relative to a specifiable enemy’. So long as there is a multinational political will in the West to resist the Russian attempt to overthrow the government of Ukraine and occupy large swathes of its territory, then the indirect provision of weapons by an alliance like NATO may just be the way that Ukrainian sovereignty is preserved. Alliance war-fighting has just taken a very informal turn.