Ancient Greece is often considered the birthplace of democracy and the ancient bedrock of Western civilisation. It was also where an early alliance of disparate nations came together to retain their autonomy in the face of a tyrannical foreign invader. There are more than a few echoes of the Persian invasion of Greece in the fifth century – and the alliance of Greek city states in response – in today’s Russian invasion of Ukraine and NATO’s robust reaction.

Depicted dramatically in the poetry of Aeschylus, his play Persians, produced in 472 BC, captures the spirit of resistance among the Greeks in opposition to the Persian threat: ‘Charge! Greek men, set your country free! Save your children, your wives, the holy temples of your fathers’ gods, the sacred tombs of your ancestors! Now is the time to fight for all these things!’ It is no stretch to imagine similar words coming from Ukraine’s charismatic president, Volodymyr Zelensky.

Founded in Delos in 478BC, all Greeks were invited to join the ‘Delian League’, which was organised as a reaction to the existential threat of the Persian Empire, first under Darius the Great and then his son, Xerxes. The confrontation with huge Persian empire began when Greek cities on the eastern side of the Aegean Sea revolted against Persian dominance in the sixth century BC. The Ionian revolt, triggered by the emergence of democratic governance in these cities, was supported by Athens and Eretria.

Despite Darius having subdued the revolt, the emperor was determined to punish the Greeks for destabilising his empire, and he launched an invasion of mainland Greece in the 490s. Despite having conquered Macedon and Thrace, Persia was ultimately defeated in the battle of Marathon. Following his father’s death, Persian emperor Xerxes instigated a second invasion in 480, conquering huge swathes of Greece, but he was ultimately defeated in the decisive naval battle of Salamis.

The alliance that formed to confront the Persian invasion and ultimately preserve the autonomy of city-states in Greece would become known as the Delian League. Despite Persia’s defeat, it is not surprising that the alliance lived on given the power of the Persian empire and the recent memory of successive invasions.  Representatives of the members of the Delian alliance met annually on Delos, with each state having an equal vote. The League’s treasury was also housed on the island, in the temple of Apollo.

In the years following its foundation, the alliance worked to chip away at Persia’s presence in the region, including the expulsion of a garrison from Thrace and a major victory in 467-466 that drove out Persian garrisons along the southern coast of Anatolia. Following a split with Sparta in 461 and the transfer of its treasury to Athens, the alliance effectively transformed into an Athenian empire. Athenian dominance of the League and reaction against its growing imperial policy began as early as 472, including a revolt by Thrace and anti-Athenian movements in states such as Miletus and Colophon. Athens interfered in the law and politics of other members of the alliance and used the League’s treasury for its own purposes. Following Athens’ defeat by Sparta in 405, the League was finally disbanded.

It is easy to think of the fate of the Delian League as a cautionary tale, and there are undoubtedly many parallels. The USSR and now Russia are imperialist, authoritarian states willing to expend enormous resources primarily for the maintenance and growth of prestige. In the absence of democratic legitimacy, conquest has always been a booster for tyrants. On the other side, is a group of disparate and autonomous states, unified in common defence to a common threat.  They don’t want to live under foreign tyranny any more than the Greeks did 25 centuries earlier.

There are distinctions, however, which suggest the NATO alliance is more enduring than its classical forerunner. First, the US has not become an aggressive hegemon within the alliance, where NATO member states have retained complete autonomy throughout the seven decades of the alliance’s existence. Unlike Athens, which began to use resources from other states, which had been contributed as part of the alliance for imperial aims, the US has long been in the position of demanding NATO members increase their domestic defence spending. Only a minority of member states, including the UK, spend the NATO benchmark of two per cent GDP on defence, earning the ire of former US President Trump. Last month, one of NATO’s wealthiest members, Canada, was publicly taken to task for falling short. One of its members, Turkey, has often strayed from NATO’s approach and has signed defence pacts with Russia in the recent past. The US is far from an imperial hegemon in this alliance, in contrast to fifth-century Athens. In fact, the US is more likely to retreat from the NATO alliance than seek greater dominance in it.

Second, all members of the NATO alliance are democracies, even though in recent years some countries have been backsliding. The contesting of the US election in 2020 by former President Trump and the erosion of democratic institutions in Turkey and Hungary are concerning and could challenge the long-term integrity of NATO. These countries are still democracies, however, as witnessed by the largely free (if not entirely fair) elections in Turkey in May. The Delian League was not composed of city-states which espoused the same form of democracy as Athens. Most apparently, Sparta, which operated under an extreme form of authoritarianism and ultimately rejected Athens’ leadership. It’s not clear what understanding Kremlin strategists have of the Classical World, but their strategy to destabilise and delegitimise democratic institutions within NATO states is undoubtedly driven by a desire to undermine the alliance itself. As witnessed by discomfort within the EU about Hungary, it is clear that systemic political dissimilarity could become a symptom of disunity.

There are other important distinctions, including that many Greek city-states ultimately ended up contributing only funds, rather than soldiers and assets, to Athens and the Delian League. Togetherness must never become tribute, and the contributions of many NATO states to forward operating positions in the Baltics and Eastern Europe is evidence that NATO is willing to commit blood as well as treasure.

There is a danger in drawing too many romantic parallels between history and the present, but this does not mean there aren’t important lessons to be learnt. The collapse of the Delian League, largely as a consequence of Athenian overreach, both validates the US’s comparatively ‘light-touch’ approach to NATO, but also underscores the importance of defending democracy in the face of Russian disinformation and interference.  NATO has become more unified than ever in response to Russia’s invasion of Ukraine, but the Delian League teaches us that such an alliance is at its strongest when members are aligned, but autonomous.