NATO has a great deal to learn from Russia's invasion of Ukraine. One of the smaller learning points is that the move to 5.56mm rounds really was a huge error as the assumption one wounded soldier temporarily removes 3 from the battlefield simply doesn't apply when fighting non-NATO forces. 22 SAS pointed this out in a report nearly two decades ago, from experience in the USA's WOT, but no one seems to have paid any attention. No doubt no one will pay any attention this time round, either, especially when far more significant lessons are also not being learned (e.g. endless passivity in the face of aggression is a very sub-optimal posture).