Bede, writing forty-six years later, says that from the time of this overthrow the power of the Northumbrian Angles began to decline, and the Picts recovered some of their territory which had been in the possession of the Angles, as well as some which had been taken from them by the Scots. The ancient territory of Northumbria extended to the Firth of Forth. Skene identifies the scene of the battle with a narrow pass in the Sidlaw Hills, north of the Firth of Tay. The territory which the Picts recovered from the Angles must have been between these two firths, corresponding to the modern Fifeshire; and this is apparent from a further statement by Bede. Among the English fugitives from the lost territory, he says, was Bishop Trumwine, who had been made bishop over the English settlers, and who withdrew along with his people who were in the monastery of Abercorn. Abercorn is near the Forth Bridge, about ten miles west of Edinburgh. If the Anglian bishop and his people were forced to abandon this place, it is clear that the recovered Pictish territory reached the Firth of Forth on the opposite side, the north side. But, writing forty-six years after these events, Bede calls the Firth of Forth "the arm of the sea which parts the lands of the Angles and the Scots," not the lands of the Angles and the Picts. Consequently, within those forty-six years, the Scots, who a little earlier appear to have held little or nothing of the mainland outside of Argyleshire, must have extended their power eastward into Fifeshire, occupying that district from which the Picts had expelled the encroaching Angles.