This fragment belongs to chapter 23 of his book andthe main theme of it is the conquest of Britain by the Saxons. The Saxons came to Britain, as the text says, invited by Vortigern, the British king. Vortigern was very overwhelmed because the northernnations was invading his territories so, he didn't find another option that called the Saxons, a fact extremely unlucky because at first Saxons wanted to help Vortigern but after a while they willdecide to conquer Britain.
Conquer of Britain by the Saxons began in 367 with a combined attack of Caledonians and Saxons but is not until 450 that Essex, Kent and Sussex were conquered. However,between 490 and 503 toke place a great victory over the Saxons, at Mount Badon, starring by the King Arthur. Nevertheless, Saxons got to take the power of the major part of Britain.
Saxons, according tothe author that is too subjective, were wolves with sharp talons that come to Britain with three ships to plunder and despoil the island in one hundred and fifty years. It's probably that Saxons werestrong people because the Saxons that came to Britain were warrior who pretended conquer a territory, so they had to be powerful. But Gildas was Celtic so it's normal that in some aspects of the texthe was exaggerating.
When Britain was conquered came to her a lot of Saxons who settled there and they took a lifestyle rather characteristic. Saxons received an allowance of provision by Britons notto attack their territories. But finally they didn't content with that provisions and they decided to plunder the whole island, in that moment, the policy of treaties conducted so far was broken....