Russia has launched a war that will reshape the balance of power and potentially transform the international system. Europe now finds itself confronted with first principles of state behavior. According to international law, Ukraine’s self-defense campaign against Vladimir Putin’s unprovoked attack checks all the boxes of a “just-cause war.”

So regardless of how Ukraine’s tragedy unfolds, the West must ask, and honestly answer, how it got to the point where cities are being bombed, soldiers and civilians are dying, and options for response are limited. Putin chose to attack Ukraine at what he must have judged to be the most propitious time for Moscow. The move was neither sudden nor provoked, as some have argued, by his fear of continued NATO enlargement or of democracy succeeding in Ukraine.

Rather, it marks the culmination of almost two decades of policy aimed at reconstructing the Russian empire and bringing Russia back into European politics as one of the principal players empowered to shape the Continent’s future. To get to this point, Putin has exploited two trends:

America’s post-9/11 preoccupation with counterterrorism campaigns and “nation-building” projects that ate up billions of dollars in spending, and Europe’s decision to move away from coal and nuclear power, while declaring natural gas a “clean” fuel and a “gateway to renewables,” as part of its climate policy.

Most importantly, European discussions on how to address climate change set aside the national security considerations of such a radical realignment of the energy mix. The two gas pipelines, Nord Stream 1 and Nord Stream 2, which bypass ones running through Ukraine and Eastern Europe, have become practical and symbolic manifestations of a flawed EU climate policy.