Out of the blue, an image is turning up all over social media. It shows a hand holding a white bird, with Swedish words that translate as ‘a Swede holds the gull’. But the words, en svensk håller truten, also mean ‘a Swede shuts up’. The poster dates back to the Second World War, when governments constantly reminded their citizens to watch their mouths. Today Western governments faced with aggression by hostile countries need their citizens to be judicious with the information they share. But national security is clashing with a culture of obsessive information-sharing.

‘Does anyone know what’s happening? JAS planes flying in over Gotland?’ a Swedish Twitter user named Eva asked on 12 January. She didn’t have much luck. Almost immediately after she posted her question, another user responded: ‘Google “en svensk håller truten”. I.E. Don’t write on the internet what the Swedish military does.’ Another user posted a picture of a blue-and-yellow-striped tiger. The tiger, made famous by Second World War propaganda, is accompanied by the words ‘a Swedish tiger’, en svensk tiger. In Swedish, the words also mean ‘a Swede stays silent.’

Most ordinary Europeans – indeed, most twenty-first century citizens – are less security-aware than the two Swedes responding to their hapless countrywoman. Indeed, many post every waking thought on social media. Until recently, doing so entailed little risk; ever since the birth of Facebook in 2004, YouTube in 2005, Twitter in 2006, Instagram in 2010 and TikTok in 2016 we have been able to share away on social media. Today we share the silliest details of our daily lives. In fact, we can post pretty much anything bar defamation of the worst kind.

On the other side of the seriousness spectrum, outfits (some for-profit, some not) conduct open-source investigations. They make their findings available, sometimes only to clients, sometimes to the general public. Their gathering of open-source material aims to inform a group of people and is clearly not mindless sharing of information. Indeed, such investigations have, for example, uncovered US military killings of Afghan civilians. Nevertheless, even such OSINT investigations constitute sharing of information – sharing that could cause harm to national security. Of course, gathering and sharing the opposing side’s details by scouring Google Earth and similar resources, as Western sleuths are currently doing to try to understand Russia’s military intentions, can be a worthy civic contribution.

Now the national-security environment in Europe is taking a sharp turn for the worse. Ukrainians face the immediate prospect of an armed invasion, and other countries are also having to shore up the defences against a potential Russian attack. In a country such as Sweden, such preparedness involves moving military units from one end of the country to another, as happened earlier this month, when soldiers were moved from the town of Boden in the far north to the Baltic island of Gotland. Norway, meanwhile, is about to launch its largest military exercise since the Cold War. Finland too is strengthening its military preparedness. Everywhere, armed forces are preparing a bit more than usual – included in populated areas.

In the past three decades or so, soldiers have been a rare sight in European civilians’ daily life. That makes it all the more exotic and exciting to see them and their equipment. And when you see something, you should share your excitement on social media, right? Not when foreign governments are scouring the internet for precisely such pieces of information. ‘They’re gathering information about where we are, why we’re there and which units we are using,’ Jonas Olsson, a Swedish Armed Forces spokesman recently told Swedish National Radio. ‘If, say, you see military personnel or a military vessel pass through, it would be a good idea to not put that information on social media until they’ve left.’ During the Second World War, governments made exactly the same point in public-awareness campaigns. ‘Bits of careless talk are pieced together by the enemy,’ one British government poster warned, while other posters cautioned that ‘careless talk costs lives’.

Early in its first incursion into Ukraine, which began eight years ago, Russia painfully learnt about the risks of mindless information-sharing. The Kremlin denied that Russian soldiers were in Ukraine, but Ukrainian activists decided to scour social media sites for postings by Russian troops. They found numerous postings by Russian soldiers who had posted selfies or other details inadvertently proving they were in Ukraine. In 2019, the Duma passed legislation banning soldiers from using smartphones while on duty. The same year, an investigation by the NATO Stratcom Centre of Excellence, based in Riga, found that researchers could easily gather information about soldiers’ operational and personal details by monitoring their social media postings.

Today soldiers of most nationalities are more social media-savvy. For the rest of us, too, the best solution would clearly be to not put military details on social media at all. As the European security environment grows more perilous by the day, everyone would benefit if everyone else curtailed their social media sharing of matters relating to the military. To be sure, adversarial governments don’t just use social media for intelligence gathering – but social media is an easily accessible treasure trove.

But how to stop the sharing? A ban perhaps? Hardly. Some citizens would rebel by posting even more such material. Others would cry foul, decrying such a ban as a violation of free speech. And the soldiers being photographed would not be able to opt for a different location – their job is, after all, to protect all of the country.

The only answer is civic responsibility. During the past three decades, whether under governments of a centre-left or centre-right kind, Europeans have been asked to do nothing for their countries except pay taxes, obey the law, and, more recently, wear a facemask. Countries that have abolished full-scale national service – that is, almost every Western country – won’t bring it back. Governments can, however, encourage their citizens to be judicious in their sharing of sensitive information. ‘Think before you speak,’ generations of parents have told their children. Today citizens of all ages can learn to think before they post. They can learn to consider the consequences which their mindless posting may have on soldiers, on the country and thus on themselves. Sweden has a new psychological defence agency that can help tackle the task. For other countries, how about a twenty-first century versions of ‘careless talk costs lives’? Nagging does work, particularly if it’s for a good cause.