What did the Roman army first build across the country when they came to Britain?

Today we are going to consider three different types of structures built during the Roman occupation of Britain, the marching camp, the fort and the fortress.
    When the Roman army under Claudius came to Britain in the year AD 43, the first thing they did was to build a series of roads across the country dividing up the native tribes and developing lines of communication. Very soon roads stretched in bold lines across the island, defining and cutting off large areas of the countryside into smaller units so that they would be easier to police and control. The roads were first built for military reasons and were the work of soldiers as they made their way north and west across Britain. At the end of a day’s march, the soldiers would need to set up camps, sometimes for a night or two. They would put up their tents and build what has been called a marching camp to provide security during the hours of darkness. It was not a fort in the accepted sense and was only intended for a short stay.
    The marching camp was a simple earthwork, usually rectangular in plan and surrounded on all its outer sides by a shallow ditch. The material from the ditch was used to construct a bank around the enclosure which, for practical purposes, had rounded comers. On top of the bank or wall there was a fence of stakes for further protection. Each soldier always carried two stakes for this purpose. There were no gates; instead the bank curved inwards on each side of the single entrance making a corridor that could easily be defended in the event of an attack during the night. Another type of camp was almost identical in plan but it was meant for longer periods of stay and was called a semi-permanent camp. It too was rectangular, with rounded corners, and surrounded by a bank and ditch, although they would both have been wider and stronger, and the bank faced with loose stones or wood. The timber for the fence would have been cut from a nearby forest. Neither camp was meant to be a serious or permanent fortification—the purpose was temporary accommodation. Any fighting would have been carried on outside the enclosure, and the Roman soldiers with their superior weapons and discipline would have easily defeated any attackers.
    By the 3rd century AD the road building program was complete; the Romans had laid down more than 6,000 miles of road, extending into Scotland. The roads were linked by a series of forts at strategic points which were permanent quarters or garrisons from which the army could easily control any resistant tribes of native Britons. Each fort was dependent on the great road network for communication and, if necessary, for assistance. The forts were first built of wood and then rebuilt of stone; however, they were only intended as accommodation centers—any fighting would have been done outside them. The earliest ones were built during the first 300 years of the Roman occupation and were concentrated in the north of England and Wales, usually in high ground. They were offensive in purpose—that is, they offered shelter and supplies to soldiers who were better equipped and more disciplined than the warring tribes that attacked them—they were in a dominant position.
    Let us consider what one of these forts looked like. We shall discuss one of medium size, about 6 acres (2.4 hectares) in area. Small ones were about 1 hectare, whereas large forts could be up to 24 hectares in area. We tend to call these very large forts fortresses and we shall be discussing them later on. Whatever their size, however, forts were usually of the same, uniform plan. A typical fort was rectangular in shape, the long sides being one-third longer than the short sides. It had rounded comers and was built in an east-west direction. In the center of each wall was a wide gateway, flanked on either side by towers. At each of the four corners was an interior tower, square in shape. Four large, rectangular blocks occupied each quarter section of the compound, giving it a grid effect. These were the barracks or soldiers’ quarters and each block had a southern section reserved as a stable for the horses. Down the center of the compound in a north-south line were three main blocks. The most northerly of these was the food store which contained the food supplies for many months, and the most southerly was the house of the commander or military head of the fort.