I started reading up on the Vietnam War and it is surprisingly interesting! From the collapse of French rule to the assassination of Ngo Dinh Diem. My question is why wasn't the ARVN itself capable of fighting off the NVA/Viet Cong? They certainly had the strength and equipment to do so. Eisenhower and Kennedy believed the South Vietnamese government could handle the war so why were they never able to muster up a proper victory on their own? I'd really love to hear some insight from you guys on this.

From what I've read on Wikipedia, the ARVN was trained for 15 years by US military advisors and given millions in aid and equipment. Was corruption a factor? Was there a cultural barrier between the US advisors and the Vietnamese soldiers?

Bonus question: Why did Nguyen Van Thieu claim he was betrayed by the US?