"It is impossible to be a leader of the working class without knowing the whole history of the class. The leaders of the labour movement must know the history of the labour movement; without this knowledge there can be no leader, just as nowadays there can he no great general who could be victorious with the least expenditure of force unless he knew the history of strategy. The history of strategy is not a collection of recipes as to how to win a war, for a situation once described never repeats itself. But the mind of the general becomes practised in strategy by its express study; this study renders him elastic in war, permits him to observe the dangers and possibilities which the empirically trained general cannot see. The history of the labour movement does not tell us what to do, but it makes it possible to compare our position with situations which have already been experienced by our class, so that in various decisive moments we are enabled to see our path clearly, and to recognise approaching danger."