1.    The Demands of a Brave New World
The end of the Second World War in 1945 heralded an age of enormous and unprecedented expansion in scientific, technical and economic activity on an international scale. This expansion created a world unified and dominated by two forces (technology and commerce) which in their relentless progress soon generated a demand for an international language. For various reasons, most notably the economic power of the United States in the post-war world, this role fell to English. English was the key to the international currencies of technology and commerce and it became the accepted international language of technology and commerce. Then it created a new generation of learners who knew specifically why they were learning a language. For the example the doctors who needed to keep up with developments in their field. The development was accelerated by the OIL Crises of the early 1970s, which resulted in a massive flow of funds and Western expertise into the oil-rich countries. Time and money constraints created a need for cost-effective courses with clearly defined goals. English now became subject to the wishes, needs and demands of people other than language teachers

2.       A Revolution in Linguistics (Sudarma)

At the same time as the use of English which was growing up for specific needs, it also influenced the study of language itself. In the past, the purpose of Linguistics was only for the usage of the language which is well known as grammar. However, as the time goes by the early studies began to find out that the usage of language grammatically is actually different from the real life usage, one of the example is the way we speak and write the language.
It can be explained that in the real life there are some differences of the usage of language in some parts of life e.g engineering, hospital, and more. Then it developed that if the use of language varies from one situation to another, it should be possible to decide the features of specific situations and make these features as basis for learning the language. Since then, especially in the late 60’s and 70’s, the research were developed into the varieties of language. In conclusion, by analyzing linguistic characteristics of the specialist area of language study, particular group of learners could be identified. This is as the principle of ESP that “Tell me what you need English for and I will tell you the English that you need”.

3.      Focus on the Learner (Novita)

The developments in educational psychology contribute to the rise of ESP, by emphasizing the central importance of the learners and their attitudes to learning. Learners were seen to have different needs and interest, which would have an important influence on their motivation to learn and therefore on the effectiveness of their learning. This lent support to the development of courses in which relevance to the learners need and interest was paramount. The assumption underlying this approach was that the clear relevance of the English course to their needs would improve the learners’ motivation and thereby make learning better and faster. The growth of ESP was brought about by a combination of three importance factors. The expansion of demands for English to suit particular needs and developments in the fields of linguistics and educational psychology. All three factors seemed to point towards the need for increased specialization in language learning.