Death is a real and constant danger for the soldiers serving on India's Himalayan border with China, but until a deadly brawl on June 15 the only killers since 1975 have been the topography and the elements.
"We get more than 100 casualties every year just due to terrain, weather conditions, avalanches... There is constant danger," said retired Lt. General DS Hooda, who until 2016 headed India's Northern Command.
"You're talking about 14-15,000 feet (4,300-4,600 metres). It takes a huge toll on your physical and mental condition," Hooda told AFP after Monday's brutal hand-to-hand battle with fists, rocks and clubs which saw the first Indian combat deaths with China in over four decades.
In the "cold desert" of the Galwan river valley in the Ladakh region where the fighting took place, winter temperatures can plunge below minus 30 Celsius (minus 22 Fahrenheit), cracking gun barrels and seizing up machinery.
There are few roads so troops -- who are fed a special high-protein diet -- must slog through the thin air themselves, carrying their own equipment as they navigate treacherous terrain.
For those who get injured or fall sick "evacuation becomes an enormous challenge," Hooda said. Getting them to a helipad "can take hours", and as soon as night falls, it's too dangerous for helicopters to fly.
This may be why the initial death toll of three shot up to 20 late on Tuesday.
Seventeen other troops critically injured in the clashes, which lasted until after midnight, were "exposed to sub-zero temperatures in the high altitude terrain" and succumbed to their injuries, the army said.
- Cold and confused -
The terrain is so high that soldiers need time to acclimatise to their new posting or they run the risk of serious altitude sickness that can kill even a healthy young person in hours.
"For an average human being who is not a resident of that place, survival in itself is a huge challenge," said Colonel S Dinny, who until 2017 commanded an Indian battalion in the region, told AFP.
"It is one of the toughest places to serve as a soldier," he said.
Normally soldiers do a two-year posting there, broken up by periods of leave. Those who smoke quickly kick the habit.
"With such low oxygen plus the weather plus the smoking, the chances of getting a heart attack shoot up," Dinny added.
The cold and the high altitude affects eyesight, adding to troops' disorientation. Weather, which can change quickly with little warning, and the hilly terrain can impair radio communication.
Adding to the confusion is the fact that the "Line of Actual Control" (LAC) isn't properly demarcated, meaning that Indian and Chinese troops can bump into each other and believe the other side has trespassed.
"The maps have not even been exchanged so that the other person knows what someone is claiming. There are no boundary markers," said Dinny.
To avoid escalations, both sides have over the years developed detailed protocols on the procedures to follow -- while also agreeing that neither side shall open fire.
If rival patrols bump into each other, they keep their distance and unfurl banners warning each other they have left their territory and should turn back.
Apart from occasional flare-ups, when they meet, the troops conduct themselves like "professional soldiers serving their respective countries, they treat each other with that courtesy," Dinny said.
- Punch-ups -
But in recent months confrontations have increased with both sides building up troops and infrastructure. China appears to have been particularly irked by India building a new road.
China, according to New Delhi, is encroaching further into new areas, including some of the northern shore of the Pangong Tso lake and the Galwan valley which China now lays claim to in its entirety.
In May there were two punch-ups before the deadly clash in June which reportedly saw Chinese troops attack the Indians with nail-studded batons, rocks and fists.
"It is time we revisit our protocol and our rules of engagement so that any disagreements can be handled in a more military fashion rather than fighting it out like goons on the street," Hooda said.
The terrain is so high that soldiers need time to acclimatise to their new posting or they run the risk of serious altitude sickness that can kill even a healthy young person in hours
In the 'cold desert' of the Galwan river valley where Indian and Chinese troops fought a brutal hand-to-hand battle, winter temperatures can plunge below minus 30 Celsius (minus 20 Fahrenheit)
Weather, which can change quickly with little warning, and the hilly terrain can impair radio communication