When the Welsh came near Sypolis, the Irish awoke to the position of affairs.
Sypolis is the largest and most important city upon the northern shore of the Lake, and it is situated at the entrance to the neck of land that stretches out to the straits.

If the Welsh were once well posted there, the Irish could never hope to find their way to the rich and cultivated south, for it is just below Sypolis that the Lake contracts, and forms a strait in one place but a furlong wide.

The two forces thus came into collision, and while they fought and destroyed each other, Sypolis was saved.

After which, finding they were evenly matched, the Irish withdrew two days' march northwards, and the Cymry as far westwards.
But now the Irish, sailing round the outside of Wales, came likewise up through the Red Rocks, and so into the Lake, and in their turn landing, harassed the cities.

Often Welsh and Irish vessels, intending to attack the same place, have discerned each other approaching, and, turning from their proposed action, have flown at each other's throats.