Tunnels Of Củ Chi, Ho Chi Minh City, Saigon, Vietnam

American soldiers used the term "Black Echo" to describe the conditions within the tunnels. For the Viet Cong, life in the tunnels was difficult. Air, food and water were scarce and the tunnels were infested with ants, poisonous centipedes, scorpions, spiders and vermin. Most of the time, soldiers would spend the day in the tunnels working or resting and come out only at night to scavenge for supplies, tend their crops, or engage the enemy in battle. Sometimes, during periods of heavy bombing or American troop movement, they would be forced to remain underground for many days at a time. Sickness was rampant among the people living in the tunnels, especially malaria, which was the second largest cause of death next to battle wounds. A captured Viet Cong report suggests that at any given time half of a PLAF unit had malaria and that “one-hundred percent had intestinal parasites of significance".
U.S. campaigns against the tunnels
The tunnels of Củ Chi did not go unnoticed by U.S. officials. They recognized the advantages that the Viet Cong held with the tunnels, and accordingly launched several major campaigns to search out and destroy the tunnel system. Among the most important of these were Operation Crimp and Operation Cedar Falls.