Thus the whole plan of the Wars of the Roses, infinitely confused though it is in detail, involves a striking up from or down to London with perpetual action west of London, but there is never any attempt to turn a southern or a northern position by the crossing of the Lower Thames in force--at least that I can call to mind. You have the same thing earlier in the Barons’ Wars. When Henry III. wishes to make a base for himself in South England and begins by advancing on Rochester, Simon makes no attempt to cut across anywhere below London. On the contrary, he marches south from that lowest crossing, making sure of intercepting the King on his march round parallel with the coast. In the succeeding campaign the line of the Severn determines everything, and here again the Upper Thames is crossed and recrossed as well, the Lower Thames not at all; and when we come to the great Civil Wars of the seventeenth century or, as our forefathers called them, “the Great Rebellion,” you have perhaps the clearest instance since the campaign of Edmund Ironside of how the estuary of the Lower Thames determined by its obstacle the strategy of the east of England. Speaking in very general terms and from the point of view of strategy alone as distinct from the great moral and social forces at work, the Parliament won because it continuously held not only London but a great triangle of the Eastern English land; Kent in the main, and all East Anglia, and after the second year of the war Lincolnshire as well. Now imagine in the place of the estuary of the Thames continuous land communication and you will see what a difference that change would have made. Charles at the very beginning of the campaign, though he could not have besieged a town as large as London, could very probably have marched past it and chastised East Anglia, broken up its recruiting centres, etc., confident that there was open to him an alternative retreat to the west upon either side of London. Nay, he could, had he been successful in this early part of the war, in an East Anglian raid have continued that success in the south-east. He might, I imagine, have isolated London, though he could not have besieged it. As it was, the two halves of his enemy’s country divided for _his_ purposes by the Lower Thames were for _their_ purposes united by common radii converging at London and by the control of all the Lower River as a continuous avenue of transport and supply. What was still heartily Royalist in Sussex (and I believe I may count here many of the castles) was, through the action of that same obstacle, a hopelessly isolated patch which Parliament had later little difficulty in reducing. But suppress the Lower Thames and it would have given Charles a solid base for advance.