The war in South Vietnam became a “war with no front” where guerrilla fighters could not be distinguished from the local populace who might, in fact, have been guerrilla fighters. The US found itself at war with an enemy that could disappear within minutes of an attack, one that might appear at any moment on a patrol or not at all. All this was very debilitating for any US soldier out on patrol and was used to explain why massacres of innocents did take place such as the one at My Lai in 1968. US patrols were under constant psychological pressure that each step might be the last for a young US soldier. Known patrol routes were ridden with booby traps such as the infamous ‘Bouncing Betty’ or the punji traps that were found by the thousand on routes used by the US military. Known patrol routes could be booby trapped with the aforementioned punji traps or trip wires attached to a grenade or mined etc. Whatever was used, it had a debilitating impact on many US soldiers. What could not be known was if a patrol route was, in fact, booby-trapped. Many were not – but American patrols were not to know this. Guerrilla warfare was such that the unknown was often more difficult to handle than the known. The VC and NLF also had the major added advantage of knowing the lay of their land. This meant that they had the knowledge to build, for example, 250 kilometres of tunnels in the South safe in the knowledge that some might be found but the majority would be functional to the detriment of the US. http://www. pbs. org/battlefieldvietnam/guerrilla/index. html ocal forces also designed primitive weapons, some designed to frighten intruders, but others were extremely dangerous. "Punji traps" -- sharp spikes hidden in pits -- could easily disable an enemy soldier. Punjis were often deliberately contaminated to increase the risk of infection.