possessed a British hinterland into which it could expand. For
Northumbria there was Strathclyde on the west and Scotland on the
north; for Mercia there was Wales; and for Wessex there were the
British remnants in Devon and in Cornwall.

But a kingdom may have too much hinterland. Scotland taxed for
centuries the assimilative capacity of united England; it was too much
for Northumbria to digest. Northumbria's supremacy was distinguished by
the religious labours of Aidan and Cuthbert and Wilfrid in England, by
the missions of Willibrord on the Continent, and by the revival of
literature and learning under Caedmon and Bede; but it spent its
substance in efforts to conquer Scotland, and then fell a victim to the
barbaric strength of Mercia and to civil strife between its component
parts, Bernicia and Deira. Mercia was even less homogeneous than
Northumbria; it had no frontiers worth mention; and in spite of its
military prowess it could not absorb a hinterland treble the size of
the Wales which troubled Edward I. Wessex, with serviceable frontiers
consisting of the Thames, the Cotswolds, the Severn, and the sea, and
with a hinterland narrowing down to the Cornish peninsula, developed a
slower but more lasting strength. Political organization seems to have
been its forte, and it had set its own house in some sort of order
before it was summoned by Ecgberht to assume the lead in English
politics. From that day to this the sceptre has remained in his house
without a permanent break.

Some slight semblance of political unity was thus achieved, but it was
already threatened by the Northmen and Danes, who were harrying England
in much the same way as the English, three centuries earlier, had
harried Britain. The invaders were invaded because they had forsaken
the sea to fight one another on land; and then Christianity had come to