How do you write an effective and concise introduction to a history essay in an exam?

The purpose of an introduction is to show the examiner that you: understand the question being asked, can outline the various ways of approaching said question and that you have a clear argument. To do this, you need to begin with a plan. Regardless of the time given in an exam you should set aside 5 minutes for planning and then 5 minutes for writing an introduction; planning time is essential to writing an introduction that provides a clear answer to the question and is concise. When planning, one must first understand exactly what the question is asking; this includes thoroughly checking dates, names and command words in the question. Defining these terms is also important if they require further clarification. From here, you then need to write down the possible factors you will include and discuss in your essay. A-Level and GCSE history questions are normally designed to force the student to evaluate the relative importance of factors in causation, and there must be evidence of this in the introduction which comes from planning. It is best to select three that you can discuss in the most detail and then order them according to which you think provides the most convincing explanation. Your first factor will be the one you argue is the most important.
Once planning is done you can move onto writing the introduction. Follow through the thought process laid out in the plan and transform this into around 5 sentences. The first two will deal with what the question is asking and give your interpretation of what the question is asking, defining terms. The next two will then briefly explain how the two least important factors are relevant to the question but do not provide/provide an unsatisfactory answer. Your closing sentence will state your own argument describing briefly why your factor is the most important or most relevant. Taking an example from a common A-Level topic, 'What was the most important factor in causing the American Civil War?' illuminates this. First, you begin the plan and introduction with an understanding that causation can be defined as long term and short term, as well as perhaps thinking about the reasons as to why any answer to the question is disputed. Secondly, factors such as the collapse of the two-party system and westward expansion could be discussed. In the final stage of planning and the last sentence of the introduction, you could then introduce the factor of slavery and state the case, for instance, on the basis that it was a long term factor which underlay all events leading to war.