NATO’s options in Ukraine

With war raging in Ukraine, President Zelenskyy has urged NATO (the North Atlantic Treaty Organisation) and its member states for assistance. If NATO states are to adhere to international law, what options are there? And what limits are there to such actions? This article outlines how NATO has and is responding to the conflict in Ukraine and considers ways forward for the alliance as pressure mounts on it to respond with its considerable military strength.

Primary focus – defence of NATO member states

The world’s most powerful military alliance, NATO is focused on collective self-defence, as outlined in Article 5 of the North Atlantic Treaty (NATO Treaty). In the current conflict between Russia and Ukraine the focus of the alliance is therefore on potentially stepping in to defend the NATO member states that share a border with Russia and its ally Belarus.

Ukraine is not a member of NATO and neither is Russia, so Ukraine is not offered NATO’s benefit of collective security and defence. Former Soviet satellite states and recent NATO members of the Baltic states are however vulnerable. Russia has conducted airstrikes on military targets in Western Ukraine within 25km of NATO member Poland’s border.

Ukraine’s borders are also shared with Slovakia, Hungary, and Romania, that are NATO member states. Other NATO states sharing land borders with Russia include Norway and the former Soviet Republics of Estonia, Latvia, and Lithuania. If any of these countries were attacked, then NATO would be obligated to intervene in line with Article 5 of the NATO Treaty. There are particular concerns over the narrow Suwalki corridor, which connects Poland with Lithuania, separating Kaliningrad, a Russian enclave and Belarus.

On 24 March, it was agreed that NATO would establish four new multinational battlegroups in Bulgaria, Hungary, Romania and Slovakia which join the four already in the Baltic countries and Poland. There are also currently 40,000 troops as well as significant air and naval assets under direct NATO command in eastern alliance countries. 

Assistance to Ukraine

President Zelenskyy has called on NATO to provide ‘effective and unrestricted’ support to Ukraine, and though not a member of NATO, the alliance has been assisting Ukraine for some time as a partner country. Requests that NATO assist Ukraine are particularly sensitive as Russia sees NATO as an encroaching threat and thus a major cause of its current conflict with Ukraine.

NATO has so far provided diplomatic, political, military, economic and other practical assistance. At the diplomatic level, NATO called on Russia to cease its military action and withdraw its forces from Ukraine, and in February 2022, NATO member states agreed to adopt economic sanctions against Russia, which was an unprecedented move.

NATO is also providing political and practical support to Ukraine which includes supporting NATO states in delivering humanitarian and non-lethal aid. Individual NATO members are supporting the international investigation of atrocities in Ukraine by providing legal expertise, but perhaps the greatest indirect form of support lies in assisting the influx of refugees from Ukraine, with Poland alone having provided refuge to more than 2.3 million people, according to the UN Refugee Agency. Individual NATO members are also supporting Ukraine through providing weapons, ammunition, training and other military aid including cybersecurity.

Photo of NATO Ukraine Commission Meeting

NATO North Atlantic Treaty Organization/

What are the limits?

Direct military intervention by NATO is problematic legally. Article 5 of the NATO Treaty is for self-defence and applies only to member states. NATO has therefore said that it will not intervene militarily in the conflict between Ukraine and Russia.

NATO can take part in interventions outside its collective defensive aim, however in the past these interventions have normally been authorised by the UN Security Council, for example in the case of NATO’s 2011 no-fly zone established over Libya.

Similarly in 1992, NATO monitored the UN no-fly zone over Bosnia and Herzegovina, with the UN Security Council authorising the enforcement of the ban in 1993. In the current Ukraine situation, Russia is likely to use its UN Security Council veto to prevent such authorisation.

Action taken outside NATO’s treaty aims and without UN Security Council authorisation would be considered offensive rather than defensive action and thus in violation of international law. For example, the 1999 NATO bombing of Kosovo was done without UN Security Council authorisation and is argued to be a violation of international law. States often ignore international law when they decide that doing so is necessary to preserve their security.

There are some exceptions to the general prohibition in international law against using force against another state. States can act both independently and collectively in self-defence (Article 51 UN Charter) in response to an armed attack. Even if states are a member of a bloc such as NATO, they can still legally act in self-defence independent of that bloc, so NATO members could legally intervene if Ukraine requests collective self-defence – which it has repeatedly done.

A priority for Ukraine has been for NATO to establish a no-fly zone over Ukraine which has been requested, to protect Ukrainian civilians from the bombing (although not artillery bombardment) of civilian infrastructure and population centres. However, such a no-fly zone would entail NATO using force to establish air superiority involving NATO aircraft and missiles engaging Russian aircraft and air defences which NATO has said would lead to direct conflict with Russia.

Russia’s position

International law notwithstanding, there are major practical risks to manage in this type of involvement. Firstly, there is the need to ensure that NATO’s concept of assistance by ‘actions that fall short of war’ align with Russia’s.

Russia has a broader concept of war-like operations than the West and by Russia’s definition, NATO’s actions may be considered direct acts of aggression. The Russian foreign minister has already stated that shipments of military equipment from other countries into Ukraine may be considered ‘legitimate targets’, while President Putin has said that a no-fly zone would be seen as a ‘participation in the armed conflict’. In such an event, Russia may attempt to destroy supply lines in Western Ukraine which could easily result in accidental or deliberate strikes over the border of a NATO state amounting to an armed attack.

Secondly, a direct military intervention by a NATO member state in the conflict risks an armed retaliation from Russia which could in turn trigger Article 5 NATO Treaty obligations and escalate the conflict with Russia (which no one needs reminding, is a nuclear armed state). NATO is therefore currently cautiously balancing international law, the practical and moral imperative of supporting Ukraine and the risk of escalating this conflict into a European wide war.


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