The senior NATO commander overseeing Exercise Trident Juncture says the exercise is relevant and worth the money.
NATO's biggest military exercise since the end of the Cold War is taking place in Norway and concludes on 23 November.
It involves more than 50,000 troops, 65 ships and 250 aircraft from across the alliance, including 2,700 personnel from the UK.
Members of the different militaries are taking part in activities designed to help them acclimatise to sub-zero temperatures.
After getting used to driving large vehicles in slippery conditions, personnel tackled a test involving being up to their shoulders in near-freezing water in just their underwear.
The entire exercise is based around a fictitious attack on Norway's sovereignty, resulting in Article Five of the North Atlantic Treaty being triggered.
US Navy Admiral James Foggo, the senior NATO commander overseeing Trident Juncture said:
"The exercise shows NATO is flexible, responsive, united and strong."
The exercise is testing NATO's collective capacity and capability to respond.
Admiral Foggo was asked by the Press Association if an exercise the scale of Trident Juncture is worth the time, effort and expenditure. Admiral Fogg said:
" It has incredible training value. It's important for us to demonstrate our capacity and our capability and our military mobility, in other words in order to deter you must be present."
He went on to say "In order to be present you have to move large numbers of equipment and personnel very quickly, you have to be agile and flexible in the field. We proved we could get there quickly." He added:
"There is a very strong message there that NATO can move all this equipment, the equivalent of seven brigades in 30 days, that is impressive."
NATO Secretary-General Jens Stoltenberg has made it clear that Operation Trident Juncture is a "defensive exercise" and is "not directed against any country".
But Russia, which thinks NATO is acting provocatively, recently revealed its navy plans to test missiles between November 1-3 in the international waters off western Norway.