You should start thinking about essay structure when planning your answer. Break the essay down into intro, 3 or 4 paragraphs and a conclusion. The purpose of the into is to 'unpick' the question - discuss key words and define them, highlight any assumptions the question makes and don't be afraid to challenge them! Also mention your ultimate argument/answer to the question and outline each 'sub-argument'/factor which you will draw on to help argue your point. Each paragraph should be a discussion of ONE point/'sub-argument'. You can arrange them thematically, so each paragraph covers a different factor. You should be able to summarise (to yourself) the argument in each paragraph in one or two sentences - this will ensure your point is concise, focused and clear. The structure of each individual paragraph is also very important - outline the main point you are trying to make at the start and the end of each paragraph. Use the bulk of the paragraph to include evidence and historians' opinions which support your point and keep analysing the importance/relevance of these as you mention them - ask yourself: why do I think this piece of evidence supports my argument? The conclusion is an opportunity to bring all of your sub-arguments/points together and re-enforce your overall opinion.