preached and sent preachers to the north-western and northern Picts,
but in some measure brought among them the higher civilisation then
prevailing in Ireland. About the same time Kentigern, or St. Mungo,
a Briton of Wales, carried on missionary work in Strathclyde and in
Pictland, and even, it is said, sent preachers to Orkney.

In the beginning of the seventh century King Aethelfrith of
Northumbria had cut the people of the Britons, who held the whole of
west Britain from Devon to the Clyde, into two, the northern portion
becoming the Britons of Strathclyde; and the same king defeated Aidan,
king of the Scots of Argyll, at Degsastan near Jedburgh, though Aidan
survived, and, with the help of Columba, re-established the power of
the Scots in Argyll.

About the year 664, the wars in the south with Northumbria resulted in
the introduction by its king Oswy into south Pictland of the Catholic
instead of the Columban Church, a change which Nechtan, king of the
Southern Picts, afterwards confirmed, and which long afterwards led
to the abandonment throughout Scotland of the Pictish and Columban
systems, and to the adoption in their place of the wider and broader
culture, and the politically superior organisation and stricter
discipline of the Catholic Church, as new bishoprics were gradually
founded throughout Scotland by its successive kings.[10]

Meantime, during the centuries which elapsed before the Catholic
Church reached the extreme north of Scotland, the Pictish and Columban
churches held the field, as rivals, there, and probably never wholly
perished in Norse times even in Caithness and Sutherland.

During these centuries there were constant wars among the Picts