Fighting at sea level is tough, but it doesn’t get any easier thousands of feet up a mountain.
The military prepares for fights at altitude by training extensively in challenging weather and terrain.
Here are 15 photos that show what it’s like.
SEE ALSO: These are 4 of the weirdest military failures in recent memory
1. Narrow passes of ice-covered rocks

2. Getting down the mountain is faster – but more dangerous – than climbing up.

3. Helicopters can make a big difference when they’re available.

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