In 1963, the American commander reported that the ARVN - the South Vietnamese army - were "ill-equipped local militia who more often than not were killed asleep in their defensive positions".
US advisers believed that good government and an efficient, large-scale war would defeat the Vietcong.
4. The US was attacked
The North Vietnamese had attacked the USS Maddox in August 1964, and then killed US soldiers in February 1965.
Johnson became convinced that action in South Vietnam alone would never win the war: "We are swatting flies when we should be going after the manure pile."
The war in Vietnam
The Vietnam War did not seem like a fair match. The Americans, under their president, Lyndon B. Johnson, had a huge army, money and technology at their disposal - the Vietcong were an underground army, which used underground tactics.
Vietcong and American tactics
The Vietcong's tactics
They fought a , ambushing US patrols, setting booby traps and landmines, and planting bombs in towns. They mingled in with the peasants, wearing ordinary clothes. The Americans couldn't identify who the enemy was.
They were supplied with rockets and weapons by China and Russia. They used the Ho Chi Minh Trail - a jungle route through Laos and Cambodia - to supply their armies. The Americans couldn't attack their supply routes without escalating the war.
Their tactic was "hanging onto the belts" of the Americans - staying so close to the Americans so they could not use air or artillery backup without killing their own men.
The Americans' tactics
They fought a hi-tech war, using B52 bombers, artillery, helicopters, napalm and defoliants (Agent Orange). This killed many innocent civilians, and failed to stop the Vietcong guerrillas.
They forced the peasants to leave Vietcong-controlled areas and made them live in defended strategic hamlets in loyal areas. This created immense opposition, and allowed Vietcong infiltrators into loyal areas.
American troops were sent on patrols, then supported by air and artillery when attacked. This demoralised the soldiers, who realised they were being used just as bait.
Search and destroy patrols went out looking for "Charlie", as they called the Vietcong. But the patrols were very visible, and easy to ambush. This led to atrocities such as "zippo raids" to burn villages, and the unprovoked massacre of peaceful villagers at My Lai in 1968.
The US gets out
The Americans didn't leave Vietnam until 1973 - by which time 58,000 US soldiers had lost their lives. Vietnam had been a total disaster for America - financially, politically and morally.
The US gets out of Vietnam
Why did America lose the war?
Take a look at this table highlighting the differences between the Americans and the Vietcong.
Why did the war arouse so much opposition in America?
58,000 Americans - average age 19 - were killed.
It was hard for Americans to believe that they were defending America by fighting in a war 8,000 miles away.
Extensive media coverage brought all the failures and horrors of the war into US homes.
Atrocities such as the massacre at undermined the moral authority of the US to continue the war.
The cost of the war meant that the US president Lyndon B. Johnson had to cancel his Great Society programme of reform.
The war was opposed particularly by Martin Luther King and by America's black community (because wealthier white men could avoid the draft by going to university or to Canada, and young black men were twice as likely to be killed).
The Vietnam War memorial in Washington DC
After the Vietnam War
In 1975, two years after the Americans left, South Vietnam was united with the North - it was now a communist state.
