Training, even “War games”, is not war. Tactics, strategy, and equipment are made as real as possible, but there is NO live ammunition flying about. Weapons are being carried, but not actually firing rounds.
“War games”, though, can have its share of casualties. Big dangerous machinery out there moving around, and not everybody is equally alert. And there are failures of even the best protocols.
In "war games", you're working with dangerous equipment in hazardous situations.
In "war", people are trying their damndest to KILL YOU.