The right answer is The Vietnamese terrain and climate were harsh and difficult.
After a long resistance from the Vietnamese, the US government gave in to political and popular pressures and withdrew from the conflict. This measure allowed communist North Vietnam to invade and conquer South Vietnam, unifying the nation. With a smaller army and worse equipped, the Vietnamese, who had a great knowledge under their territory, avoided great confrontations making strategic escapes by their areas. In addition, they encouraged the morale of their soldiers with the constant deaths of American soldiers, mainly through jungle traps. Ordinary and improvised mines were scattered throughout the jungle, especially around fallen trees. The traditional mines were triggered when one stepped on one of them and removed his foot. The improvised ones, however, contained a rifle cartridge that, when pressed, was pressed against a pin that detonated and fired.
