Here’s some advice: Before antagonizing Russia, check the weather. Napoleon, Hitler, and other would-be conquerors reaped disaster after failing to tune in to the forecast. Despite these lessons, Europe is about to repeat history. To avoid armed conflict, Europe needs to fight Putin’s war not with weapons, but with the power of free trade and a working knowledge of Russian history.

A popular misconception about Russia’s invasion of Ukraine is that the captured territory will be used as a base from which to attack the rest of Europe. Russian President Vladimir Putin denies the claim, noting that the motivation for hostilities in Ukraine is not out of desire to antagonize Europe, but to protect his borders and shelter ethnic Russians. This sounds reassuring, but presidents who have presided for 16 years are seldom honest. Perhaps Putin’s soothing words are nothing more than political rhetoric.

A glance at a map proves that Putin has been shockingly transparent. After an initial westward feint, Putin has confined his attacks to Eastern Ukraine, which is home to the country’s highest concentration of ethnic Russians. The West has nearly forgotten that this land once belonged to Russia, not the Soviet Union, until the Bolsheviks ceded the territory in 1920. If Putin’s goal is what he claims—that is, to protect “people living in the south-west of what has historically been Russian land, [who] have called themselves Russians and Orthodox Christians”—he is doing exactly what would be expected.

This is good news for non-Ukrainians worried about invasion. Without control of Western Ukraine, Putin is not positioned to launch attacks on the rest of Europe. Realizing this has given many European countries a false sense of security.

Unfortunately, the map has more to tell.

Donetsk, the furthest-westward region Russia occupies, is Ukraine’s top supplier of coal. The area is sufficiently rich in natural resources to sustain energy independence in Ukraine. Other forms of “greener” energy aren’t enough to keep its economy afloat. Without this land, Ukraine is crippled. That is Putin’s secondary reason for targeting this region. It should also be a warning.

Using the climate to fight battles is nothing new for Russia. But this time its weapon of choice isn’t frosty winters; it’s a deadly heat wave.

Hydroelectricity requires water, but Europe’s skies are cloudless. Biofuel requires crops, but Europe’s soil is parched. Nuclear power requires rivers to cool reactors, but Europe’s rivers are dry. Green energy fails when water is scarce. Europe has positioned itself to rely solely on green energy when it can’t get fossil fuel, and it has made itself dependent on Russian oil by prohibiting drilling in its own territory to protect the environment.

This has given Putin an unparalleled opportunity to squeeze Europe into submission by taking advantage of a broiling summer. Heat does not require Putin to declare war. It violates no laws. But people are suffering and dying in record-breaking high temperatures—for green energy’s sake.

Europe: Incentivize producers to drill oil by promising them that they will still have a business when proposed green energy laws go into effect. Let the market power air conditioners first, and then start thinking about how to build a greener world.