"The NATO way of land warfare has never been seriously tested against a major state adversary," one expert told Newsweek.

Turns out that fighting a peer competitor is very different from bombing defenceless people

The NATO style of fighting, so heavily reliant on controlling the skies, has also only been tested in recent years in arenas where the alliance had air superiority, experts say.

"No living member of NATO armed forces has experienced combat close to what Ukrainians have experienced over the past 18 months," Davis Ellison, a strategic analyst with the Hague Center for Security Studies (HCSS), told Newsweek.

"The NATO way of land warfare has never been seriously tested against a major state adversary, despite decades of investment and training," he added.