Today marks the start of Russia’s quadrennial Zapad military exercise. As always, NATO will be closely watching the massive drill involving not just Russia but Belarus and selected other guests as well. But this time, don’t just look for soldiers approaching NATO borders. Nation-state aggression is changing, and the aggressor can experiment by creating new cocktails of aggression.

Until 16 September, some 200,000 troops from Russia, Belarus, India, Serbia, and a handful other countries will conduct a mock defense of Russia’s West and Belarus. But even though Zapad (which means “West” in Russian) is labeled as a defensive exercise, Russia’s and Belarus’s neighbours are wary. “What raises our concern is the Russian and Belarusian lack of transparency,” Latvia’s defense minister, Artis Pabriks, told me. “We observe continuous manipulations of information with regard to the true number of participants as well as the true scenarios and objectives of the exercise. And previous exercises have involved aggressive scenarios against NATO, including the Baltic states and Poland.”

Indeed, the geopolitical atmosphere is considerably worse than was the case when the last Zapad exercise took place four years ago. Since then, Russia has used novichok to kill civilians in the UK and been punished by the West. It has imprisoned Alexey Navalny and been sanctioned again. Belarus has deviously diverted a Ryanair flight and likewise been sanctioned. And Belarus is hitting back. Soon after the EU banned EU-bound flights from using Belarusian airspace following the Ryanair incident, President Alexander Lukashenko vowed to “flood the EU with migrants and drugs”. He’s since arranged for thousands of people from Iraq and other countries to travel to Belarus and then cross the border into Lithuania, Latvia, and Poland. The devious scheme has already forced Lithuania to erect a border fence and all three countries to declare a state of emergency.

Lithuania, Latvia, and Poland can see the migrants approaching their borders, sometimes accompanied by Belarusian officials. Because migrants are not the sort of attack NATO had in mind when writing its famous Article 5 on collective defence, NATO is not going to hit back. But in so-called “grey zone” aggression, as in medicine, prevention is the best cure. By spotting schemes early, targeted countries can blunt their impact.

Now consider how Russia and Belarus might take advantage of the fog generated by a massive military exercise. “The Zapad drills are not taking place for the first time, but this time they’re taking place in a sensitive context due to the weaponised illegal migration led by Lukashenko’s regime,” says Andrius Kubilius, a member of the European Parliament and two-time former prime minister of Lithuania. “The Kremlin likes to create a sense of intimidation, but we are not easily scared.”

But how to know what to prepare for if the other side can innovate without constraints? Before Lukashenko’s migrant scheme, a sinister plot involving migrants flown in and dropped off at a neighbouring country’s border appeared impossible. It wasn’t. Imagine if Belarus uses Zapad to launch more such schemes in the same manner it has done with refugees from Iraq. Baltic governments already have indications it’s trying to do so, and there are plenty of unscrupulous regimes that would be only too happy to get rid of a few thousand citizens. Heaven forbid Lukashenko works out a scheme with the Taliban to weaponise desperate Afghans vis-à-vis NATO.

Or should countries prepare for China, invited by Russia as an official Zapad observer, surreptitiously blocking trade with Lithuania, a country it’s trying to punish for supporting Taiwan? Last month China underhandedly suspended imports of Lithuanian agricultural goods. Should the international community instead be concerned that Lukashenko might manufacture a natural disaster involving one of his country’s infamously unsafe power plants? All of the above, and more, is possible, but prediction is not. That makes constant monitoring vital.

Zapad returns every four years, just like NATO regularly conducts exercises, the latter doing so more transparently. Every time each side closely monitors the other. Zapad 2017 was a rather standard iteration of the exercise, though it did involve GPS being knocked out in northern Finland and Norway, which forced airliners and fishing boats in those regions to resort to manual navigation. Since then, Russia had become a truly innovative practitioner of aggression below the threshold of war. Belarus, no longer concerned about its international reputation, can go all-in using devious means against the West.

This means it’s no longer enough to keep an alert eye on what Russia’s military and its friends are up to this month. On the contrary, a massive military exercise can be used to amplify grey zone aggression. Consider how China may use upcoming military exercises to also try out non-military tricks. “Unpredictable and opportunistic actions could potentially lead to undesired escalation,” Pabriks points out. Those who simply look for movement of Russian armoured vehicles this month may miss the real action.