The earliest forms of castles on the Gower Peninsula were 6th Century BC earth and timber fortifications built high upon hilltops and coastal promontories. These forts were quite sizable constructs and were designed to defend against small impending tribal attacks. With the later invasion of the Romans, however, these early Gower forts had little chance of defending their occupants against the scale of ingenuity and sophistication shown by the Roman army. After easily overcoming these primitive defenses, the Romans showed little interest in Gower other than securing rulership of the area - concentrating their efforts instead upon other areas of South Wales.
The Romans finally retreated from Gower in the beginning of the 5th century AD. With their departure, the country as a whole found itself open to hostile bids for rulership from other nations. It was not long before the Saxons began their rampage through the east of England, whilst both the Normans and the Vikings also set their eyes on this sceptred isle. Despite these raging battles for power across the whole of the UK, the people of Gower somehow managed to return to their simple settlement lifestyle - with only the occasional Viking attack interrupting their day to day routine.
It wasn't until the early 1100's that the Norman's, having overrun the Saxons in 1066, decided to extend their rule to the Welsh and turned their full might against Swansea and Gower. The King of England, Henry I, quickly realised the potential of the natural port at Swansea and seized the whole of Gower from the Welsh inhabitants, renaming the area from its Welsh name of Gwyr to Gower. The king then gave his most trusted friend, the Earl of Warwick, Henry de Beaumont (Newburgh), the lordship of Gower to maintain. In order to protect the port at Swansea from invaders, such as the persistent Vikings, Henry de Beaumont erected a castle to oversee the River Tawe and to become his headquarters, or caput. This became Swansea Castle.
Originally, the Norman castles built at this time were constructed of strongly-fortified timber, rather than the much stronger stone buildings that have survived to this day. More commonly, the Normans built their castles using the 'motte and bailey' method. This consisted of a mound (motte), either natural or man-made, whereupon a wooden keep would be erected. This would then be surrounded by a flat area (bailey), which was defended by a ditch, bank or some other enclosure. But in the vast majority of cases in Gower the castles had been constructed using the 'ringwork' method which, although similar to the 'motte and bailey' method, was designed to take full advantage of the natural landscape and its potential for defense strategy.
As the years passed, these fortifications were either strengthened and rebuilt using stone and masonry, or were left to fall apart if they were no longer deemed useful. After the Welsh rebellion, led by Owain Glyndwr during the early 1400's, had destroyed much of the remaining Gower Castles and liberated the Welsh from Norman rule, the only castles which continued to be occupied were the fortified manor houses, such as Weobley and Oxwich Castle.