Across the Zuiderzee, which is today Lake IJsselmeer, lay the Frisian territories of Westergo and Oostergo (the borders of which approximately coincide with the present-day Dutch province of Friesland.
When emperor Frederick Barbarossa travelled to the Netherlands in 1165, to settle the dispute between the counts of Holland and the bishops of Utrecht over the Frisian territories, he came up with a solution which was virtually guaranteed to keep things as they were.