It is easy to forget that defence and security are not the same thing. Defence is what countries must resort to when their security breaks down.
And during peacetime, countries spend money on defence precisely because they fear for their security.
Since 2014, the security environment for the European Union has deteriorated sharply. In March of that year, Russia invaded Ukraine and annexed Crimea.
It was the first time since the Second World War that a major European power sought to redraw its own borders by force of arms.
In 1994, Russia agreed to defend Ukraine’s territorial integrity in exchange for Ukraine’s handover of the nuclear weapons it had inherited from the Soviet Union.
But Russia didn’t stop with Crimea; since then, it has waged a low-intensity unconventional war against Ukraine in the country’s eastern Donbas region.
And Ukraine is not alone. Russia has also sent ships and warplanes to threaten the coasts of other Western countries, abducted an Estonian intelligence officer on Nato territory, and sustained an ongoing military buildup in Eastern Europe, the Arctic, and elsewhere.
Despite these deteriorating security conditions, a slim majority of Britons voted in June 2016 to withdraw from the EU — a decision that could fatally undermine the UK’s relationship with its European Nato partners.
Making matters worse, in November of 2016, Donald Trump, who has long expressed admiration for Russian president Vladimir Putin, was elected president of the US.
Although Trump expressed disdain for Nato during the 2016 campaign, he appears to have been reined in by the many generals he has installed in top positions.
Still, he could always change his mind.
The Republican Party is in the throes of a deep internal schism that could end with the victory of its populist wing, led by Trump’s nationalist, anti-EU Svengali, Stephen Bannon.
If Bannon does manage to transform the Republican Party in accordance with his nationalist vision, and if the Republicans retain or regain power in the future, US security commitments to Europe will no longer be reliable.
Continued Russian attacks on Western political systems, or even an outright military attack in Europe, could go unanswered by the US.
Without firm US support, a politically divided EU would be increasingly vulnerable to Russian political domination. At the same time, a politically cohesive EU would be a bulwark of stability.
In the absence of US leadership, a stable and secure EU could thus become the most important pillar of the UK’s post-Brexit security strategy.
But the stability of the EU is far from guaranteed, because a smooth and painless Brexit may tempt other member states to also quit the bloc.
Some argue that this outcome is unlikely, because it is impossible, in practice, for eurozone countries to leave.
If a eurozone country even suggested that it might withdraw from the euro and the EU, the resulting capital flight would devastate its economy.
According to this view, the fact that two-thirds of EU member states belong to the euro is enough to prevent the EU from unraveling. If only that were so.
In reality, a number of important EU members remain outside the euro, including Poland, the Czech Republic, Denmark, Romania, and Sweden.
Moreover, under favourable circumstances, eurozone countries with current-account surpluses — such as Germany, the Netherlands, Spain, and Austria — could probably leave the euro without suffering catastrophic harm.
As things stand, the UK still seems to be politically incapable of abandoning Brexit altogether, even though that would be the best course of action for all involved.
But between the options of a ‘soft’ and ‘hard’ Brexit the latter may have at least one advantage. Namely, it would not further undermine European stability, which also happens to be Britain’s biggest security asset.
To be sure, a ‘hard’ Brexit would come at a high economic cost for the UK.
Industrial supply chains would be disrupted, the construction industry would be denuded of its EU workers, the City of London would lose international importance, the pound would continue depreciating, and the public sector, particularly the National Health Service, would be stretched thin.
The EU, too, would incur costs, albeit much smaller as a share of its overall economy.
Despite the costs, a ‘hard’ Brexit would, at a minimum, discourage other EU members from following the UK’s lead, thereby shoring up European stability and helping the UK maintain its national security, which may be the most important consideration in the long run. Such an outcome would be ironic, to say the least.
But even more ironic is the fact that those pushing for it are the very Brexiteers who would like to see the EU fail.
They are convinced that their vision of a buccaneering, global Britain can be achieved only with a clean break from Europe. They might soon find out if they’re right.