On February 24, 2022, Russian armoured columns crossed Ukrainian borders from three directions — Belarus toward Kyiv, the Donbas, and Crimea — with the apparent intention of taking the capital within days and replacing the Ukrainian government. The column that stalled north of Kyiv became the war's first image. They did not take Kyiv. Four years later the war grinds on; Russia has formally annexed and partially occupies four Ukrainian provinces — Donetsk, Luhansk, Zaporizhzhia, Kherson — on top of Crimea; perhaps a million people are dead or wounded on both sides; a country of forty million has been transformed into the most heavily armed society in Europe; and the post-Cold-War security architecture of the continent has effectively ceased to exist.
The war's deeper causes go back to 1991 and the unsettled question of where Russia ends. Putin came to view NATO's eastward expansion, and Ukraine's drift westward after the 2014 Maidan revolution, as a strategic encirclement that required reversal — and the West came to view that view as a pretext for restoring an empire. Both sides were partly right. The 2014 annexation of Crimea and the proxy war in the Donbas were the dress rehearsal; the West's tepid response — limited sanctions, the half-honoured Minsk agreements — confirmed Putin in the belief that a full-scale invasion would be tolerated. He was wrong about the West, which assembled sanctions and arms transfers of a scale Moscow had not war-gamed; he was more wrong about Ukraine, whose army and society fought with an intensity that surprised every observer including its own, breaking the thrust at Kyiv and turning a planned three-day operation into a grinding war of attrition along a front of entrenchments hundreds of kilometres long. It is the largest land war in Europe since 1945, and its shocks ran outward through global energy and food markets — the severing of cheap Russian gas broke the German energy economy, and the blockade of Ukrainian grain drove hunger across import-dependent states. The war has remilitarized Europe and triggered Germany's Zeitenwende, accelerated Finland and Sweden into NATO — the opposite of Putin's aim — and demonstrated to every authoritarian state that the West is willing to fund a long war but unwilling to fight one.
How this war ends — by negotiated freeze, by Ukrainian victory, by Russian collapse, by exhausted stalemate — will set the terms of European security for the next half-century. Along the entrenched front neither side has the mass to break through cleanly, and drone warfare has rewritten the tactical manual; conscription is returning and defence budgets are climbing from Warsaw to Berlin. The energy and food shocks that rippled out in 2022 reshaped budgets and politics far beyond the battlefield. And the outcome will be read carefully in Beijing, in Tehran, and in Pyongyang as a case study of the costs and benefits of revisionist war — most pointedly over Taiwan.