The battle of Irpin narrowly saved Ukraine. Here’s how it went down.

Russian columns eventually tried to cross the Irpin at the end of February and into March. But it was too late. “Russian commanders had no option but to push forward in linear columns with ill-prepared forces into still thin, but now far more robust and prepared defenses,” the British Army Review article said.

The attempted crossings were halted by the 72nd Mechanized Brigade, some Ukrainian tanks and artillery, and hastily mobilized volunteers who learned how to operate their deadly Western-made Javelin and NLAW anti-tank missiles on the spot. “In my company, if a position had a Javelin, one soldier dug a hole while the other watched a YouTube video on how to fire it,” recalled one Ukrainian officer.

These guided missiles and artillery shredded Russian tanks and perceptions of their inpregnability.

By the end of March, Russian forces withdrew back to the north. If Russian tanks had managed to cross the Irpin and entered Kyiv, the war could have essentially ended in Russian victory within the first week.

No plan survives contact with the enemy, and unexpected snafus — what the German military philosopher Carl von Clausewitz called the “friction of war” — inevitably disrupt the cleverest of strategies, which the Kyiv assault was not. Ukraine also displayed a remarkable ability to quickly mobilize volunteers who proved effective.

Nonetheless, Collins blames the Russian failure on shoddy preparation. “It was 100 percent sloppy planning, a lack of preparation, and unexpected Ukrainian resistance that should have been anticipated,” Collins said. “The mechanized forces should have rolled through this minimal defense like a hot knife through butter.”

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds an MA in political science from Rutgers Univ. Follow him on Twitter and LinkedIn.