Thanks to Colonel Craig USMC for the tip!
"Every Man Has A Breaking Point" By Quintus Curtius
"Pressure reveals the man. Take a man, any man, and subject him to extreme stress. Subject him to sleep deprivation or fear, exhaustion, and the uncertainties of climate and personal safety, and you will see the soul of the man. This is what I always liked about extreme stress. It reveals the true essence. A young military trainee thrown into an extreme environment or hostile fire zone, or a young lawyer taking on his first big high-stakes jury trial, will both reveal their inner natures by their performance and responses to pressure."
An American soldier from the Vietnam War just prior to entry into a NVA/VC tunnel complex. The stripped soldier in reality, carrying only a flashlight and .45 caliber ACP pistol. Nothing more. What awaits that man is the unknown and great danger. Additional equipment an impediment?
OR a man entering into the underground tunnel complexes of Hamas in Gaza.
AND before the Israeli the American "tunnel rat" of the Vietnam War.
Read that account of an American soldier and his experience, into a tunnel in pursuit of an enemy, the uncertainty factor and operating alone most acute.