Why was the ground war in Vietnam so difficult to fight?A) Civilians often joined the Vietcong and U.S. soldiers often could not identify the enemy // B) There were insufficient numbers of...
Although civilians joined the Vietcong which made identification of enemies difficult, this alone was only one factor that made the ground war difficult. The United States sent plenty of ground troops -- but these were young conscripts, not professional troops, who were fighting an offensive war, as opposed to the Vietcong, who were fighting for their homes. The United States also possessed superior military technology, and completely controlled the airspace over the country. Although the bombings inflicted by the United States did widespread damage, they did not stop the Vietcong from fighting. Had they been on their own, the US certainly would have overrun the country, but the fact that China backed the North Vietnamese, sending an endless supply of men and materiel caused the US to eventually lose the war.
Of these answers the only one that is really plausible is A. C is completely untrue. D is untrue for most soldiers most of the time. You could argue that B is true, but it is a stretch.
Of course, you could argue that there were not enough ground forces. If the US had sent 5 million soldiers, it might have been enough to simply blanket Vietnam and end the war. However, this is not a feasible thing to do. As it was, the US put as many as 600,000 troops into Vietnam at a time. It is hard to argue that this is too few.
What really made the war hard was the difficulty of identifying the enemy. It was hard to know who the enemy was and therefore it was hard to destroy them. This is a major reason that is often given for the difficulty of winning the ground war in Vietnam.