Months before the Russian invasion, a team of Americans fanned out across Ukraine looking for a very specific kind of threat.

Some were soldiers, with the US Army’s Cyber Command. Others were civilian contractors and some employees of American companies that help defend critical infrastructure from the kind of cyber attacks that Russian agencies had inflicted upon Ukraine for years.

The US had been helping Ukraine bolster its cyber defenses for years, ever since an infamous 2015 attack on its power grid left part of Kyiv without electricity for hours.