Tired and short of breath. But that is how he has been all these days. The thin, oxygen-starved air saw to that. However fit and well acclimatised you are, it will leave you panting in a short while. At the posts, carrying your equipment and walking in the powdery snow, that's really gruelling.
Every step is torture.
Every breath an agonising wheeze. You sink into the snow. Despite the imported winter gear, the cold creeps into your bones. And it stays there. Fortunately for Captain Sharma, the toughest part is over.