During the Viet Nam war it was a path leading from North Vietnam to the South (passing through Cambodia as well) that was used as supply route by human porters walking for miles carrying heavy loads of weapons and ammunitions to the fighters of the South.
Named after the leader of North Vietnam, the trail was a long and complex path carved mainly through the jungle (for concealment, to avoid being spotted by aircrafts or helicopters) and used to carry supplies to the guerrilla fighters in the South.
The idea seemed anachronistic at that time when modern armies used lorries, helicopters and airplanes to take loads everywhere but in the context of the Vietnam War was very ingenious.
North Vietnam didn’t have a mechanized army or air force but had a lot of manpower; basically they couldn’t carry stuff because of the lack of vehicles but because of this they didn’t need to carry fuel, parts or heavy ammunitions only food and small arms bullets for the men!!! In addition, roads, in Viet Nam, weren’t very reliable and certainly were under continuous observation from US bombers.
Also, the idea of the trail was to lure the American army to try to sever this line of logistic supply, sending armed patrols to try to attack what was basically a narrow trail that could change every day! Infiltration and secret operations (CIA manned) were also used to try to “sneak in” and sabotage the trail using the combination of “special” forces and local armed civilians/partisans.
Basically, the hardware and manpower deployed by the US (and casualties) were enormous resulting in destroying few bicycles carrying some bags of rice and old Russian machineguns (sometimes even M16 rifles taken to the Americans!!!).
An added bonus for the North was that the US, exasperated by the “impunity” of the porters of the trail, decided to bomb and eventually to infiltrate into “neutral” Cambodia to try to neutralize the path through this nation. The result was a terrible civil war and a complete disaster that involved the population of Cambodia as well (Pol Pot and the extermination of millions of Cambodians)!