What caused great difficulty in fighting in vietnam?

There were a number of elements that made fighting in Vietnam difficult. Among these were thick jungles, lack of acclimatization of occupying forces (French then US troops), difficulty identifying the enemy (a guerrilla force that blended with the homogenous population), lack of home front support (growing social unrest and antiwar sentiment), unclear objectives, ineffective (puppet) government in South Vietnam, unsteady ally government, long supply lines (approximately 8,000 miles of ocean between the US and Vietnam, and a host of other reasons.