How old is English?
Raids and defense
The war in Vietnam proved that a
central-led army can have great difficulties in defending a territory
against raids. The word 'raid' can be replaced by 'guerilla'. The Roman
Empire relayed upon heavily defended borders: Hadrian's Wall and the
Rhine border. It was all about keeping the raiders out. Once that
border fell, everything behind it was unprotected.
The Romans had maintained at least some 14 000 men in Britain, 2 legions of 5000 men + a number of auxiliary cohorts. Of course, just like any army, this force was not permanently available. Professional soldiers also need some holiday from time to time. One can estimate that only some 6000 soldiers were working at any given time. Needless to say that in case of serious trouble, all men could be mobilised
Trouble in the London council
The southwestern lords in the council did not hail the Anglo-Saxon housecarl system. They wanted a 'proper Roman army'.
As soon as Roman rule was gone, Britain had returned to its ancestral tribal system.
Vortigern couldn't maintain unity in the council. As the eastern, north-eastern and north-western British lords (tribal leaders) had probably a numeric majority in the council, the southwestern lords (from Wiltshire to Cornwall - some Welsh lords joined them) felt threatened. Their (financial) position depended upon the access to the markets of the Roman Empire. Opposition in the council grew and declared itself pro-Roman (read: conservative). They were desperate to regain Roman protection. Some thought with nostalgia about Maximus Magnus' idea to secure protection by acquiring power in Rome itself. The majority in the council however felt that new times had arrived, and that new ways of organizing the defense of the state had to be developed. They were the independents . One additional reason for the division was that the pro-Roman party claimed more control over the German reserve troops, although this probably meant that previous agreements had to be reviewed. The discordance resulted eventually in the refusal to acknowledge the legality of the council by some of its southwestern (and Welsh) members. Vortigern managed nevertheless to keep the (Anglo-)Saxon unit in Dorchester upon Thames under the control of the council.
Eventually, Britain had a scattered self defense force of some 8000 soldiers. But circumstances were not as expected initially. 1000-1500 men fought on the side of the southwestern alliance. On the proto-English side, 6000 men at least were spread over the hazardous regions (Kent, Yorkshire, Lancashire). These 6000 men can be subdivided in about 3000 housecarls and 3000 men of the fyrd (peasant levy).
This smallness of the Anglo-Saxon armies explains why the alliance was able to defeat the Anglo-Saxons more than once. The southwest alliance could gather all their Britons against an overspill of otherwise spread Anglo-Saxons. This explains also why the alliance could never decisively win: the Anglo-Saxons always had enough reserves to form a new army.
The Anglo-Saxon mobilised a force which was eventually engaged to re-establish law and order and the unity in the country. However, the effort to restore some unity in Britain led to the opposite result. Already outnumbered in the council, more and more Welsh families joined the south-western dissidents. Northwest proto-Welsh lords however remained loyal as they knew that they were dependent for their security upon Anglo-Saxons. The Picts and Scots still represented a menace.
A civil war was at hand, but would remain limited in casualties.