Smell.

This is coolbert:

The Korean War battlefield quite often permeated by the overwhelming smell of GARLIC. Eaten by Chinese troops in enormous quantities during the winter time as a prophylactic antidote for the common cold.

AND THAT PERVASIVE SMELL OF GARLIC DETECTED BY AMERICAN TROOPS AT A DISTANCE. Even before visible contact made the American infantry man aware of and alert to the presence of Chinese troops.

To include the American infantry man the famous Hollywood actor James Garner.

As recounted by James Garner and thanks to Snopes.com:

"'[A]rmy chow was bearable as long as I could keep the onions and garlic out of it. I cannot stand onions and I'm very sensitive to garlic. I can taste tiny amounts of it, like when they've cooked another dish with garlic before and don't wash the pan. If I get even a hint of it, I might throw up in my plate.'"

"'This violent aversion may have saved my life: like our South Korean allies, the Chinese and North Korean troops lived on a diet of fish heads, rice, and garlic. One night while on guard on the line, I caught a faint whiff of it coming from the direction of the enemy positions. I couldn't see anything, but I knew there was someone out there and they were coming closer. Once I sniffed them I could hear them, too. It turned out to be a patrol heading straight for our position. They were just the other side of a rise when I passed the word down the line. We were ready for them and stopped them in their tracks.'"

That experience of James Garner hardly unique.

Consider form the book: "The Last Stand of Fox Company":

 * "Chinese units had a pungent odor that carried hundreds of yards"

* "Caffareta caught the scent of garlic before he saw them"

* "Barber . . . noted that their uniforms reeked of garlic"

* "he picked up the whiff of garlic"

ALSO THE CHINESE DURING THE KOREAN WAR REPUTED TO LUBRICATE THEIR WEAPONS WITH WHALE OIL DURING THE WINTER!

Whale oil by reputation not congealing from the cold, weapons lubricated properly, function maintained even at the lowest of temperatures.

WHALE OIL TOO POSSESSING AN OVERWHELMING AND DISGUSTING STENCH DETECTABLE AT A DISTANCE!

coolbert.