Source B has been taken from a private conversation that President Johnson was having in May 1964. He is basically saying that the situation in Vietnam is not worth fighting for and that he disagrees with going to war, although certain factors are making it very difficult for him not to go into war. As he is speaking in a private conversation, it makes what he is saying extremely reliable because he is likely to be being honest and truthful, as he does not have to put on an act in front of a group of people and he is not speaking on the radio for example so Johnson does not think that what he is saying will be disclosed to the public. Johnson sounds as if he is being honest because he is speaking in a very informal tone, as he says things like, 'it's the biggest damn mess.' He would not talk like this if he was trying to persuade someone important that he was opposed to going to war. He is presenting unofficial reasons of why America should and shouldn't go into war and they are likely to be his personal views. However, because there is no information to suggest whom he is talking to, making it less useful because he may have been speaking to someone who he wanted to believe that he was against war.
Johnson does want to make sure the Communists are dealt with and not ignored, as he says, 'if you start running from the Communists, they may chase you into your own kitchen'. This means that if the Communists are ignored, they will spread and become a threat to US lands. He is referring indirectly to the US policy of containment where Communism has to be prevented from spreading and the Domino theory. Historians can make good use of these views of the President because his views are very important, as he was one of the main leaders in the Vietnam War. The source can also be useful to suggest that Source A is inaccurate because President Johnson has given a totally different account of why America should get involved with Vietnam, which implies that one of the sources is inaccurate.
Some of the points that Johnson makes are accurate and correct, however some of the things he says are incorrect. For example, 'I don't think we can fight them ten thousand miles away from home' is inaccurate because they managed to send thousands of troops, US marines, chemical weapons and search and destroy to fight against the Vietnamese. Although he was unaware of this at the time, it still makes the source not useful for giving us factual details; its main uses lie in giving historians Johnson's opinions about going into war.
Source C is an American critic of the war, called Noam Chomsky, being interviewed in October 1982. The source could be trustworthy because Chomsky would have had access to more sources due to the interview being after the war. He will have been able to look at these and have more evidence to base his arguments on. As Chomsky is speaking in the 1980's there was more freedom of speech and he will have been able to say what he thought without him being seen as a defender of Communism or North Vietnam, as there would have been little tension and bad feeling at this time. Therefore he is likely to have been honest, which gives the source more uses to historians.
The factors that make this source untrustworthy are he is speaking in an interview so some of his answers could have been altered by the interviewer or he could have made his answers more dramatic when he talks about South Vietnam being devastated, to seek public approval. Chomsky was not involved in the war so it can be argued that he does not know much about why America got involved in Vietnam, as he was not there at the time when leaders were making decisions. He can only assume what the reasons were. This source is not useful for providing a balanced account of the reasons why America got involved with Vietnam, as he is a war critic so he is always going to be biased and against the war.
Chomsky suggests what he thinks are the real reasons for America getting involved in Vietnam and they are backed up with evidence. He states that people opposed to the war in the 1960's were accused of defending Communist North Vietnam. He is probably using this to explain why it is mainly now that people like him are expressing their views towards America's reasons for their involvement because if they spoke before they would be accused of this, and his purpose is to gain more public approval. Chomsky implies that the official reasons were incorrect by saying, 'the U.S. did not want an independent South Vietnam that was no longer dominated by America.' He is suggesting that America didn't actually want South Vietnam to have independence because America wanted to be in control and thus make sure South Vietnam would not become a superior force.
Overall, Source C is mainly useful for identifying what an American critic thought of the American reasons for getting involved, and due to some inaccuracy and over-dramatic comments, it is less trustworthy, therefore less useful. Also, there is no other viewpoint given that is suggesting reasons for America to go to war; it is simply explaining why it was wrong.
Sources A, B and C are all useful to some extent. Source A gives the official reasons for America getting involved in Vietnam, that Johnson wants the public to hear and Source B and C give the unofficial reasons. Source A is less useful for providing an accurate account of the reasons for going into war, because they are simply the reasons that the President wants the public to hear. Johnson was more likely to be telling the truth in Source B because he is speaking privately, so it makes the source useful for identifying his thoughts and feelings. Source B is also useful for proving that the President is lying in his speech (Source A) or has changed his mind, as they show very different views. Source C is very useful for providing a more accurate account, as Chomsky is a person who wasn't involved in the war so he does not have to pretend to anyone what America's reasons were. It can provide historians with useful facts that suggest that America was being selfish and was merely attacking Vietnam, not defending it. Although this source lacks some details and mentions nothing about Communism, which is the main reason America became involved. None of the sources mention anything about the Truman Doctrine or the policy of containment, which makes them less useful because no opinions about these can be gathered. The sources give the views of the President in the 1960s and of an anti-war campaigner, but not the views of the Congress or U.S. people and they do not mention why President Kennedy became involved in Vietnam in the first place. All of the sources give historians an idea as to what the reasons were, but do not provide historians with the full picture.