Question: What union was directed by a common monarch and was abandoned in 1523?
Sentence (from "History of Sweden (1523–1611)"): It began with the reconquest of Stockholm by Gustav Vasa and his men from the Danes in 1523, and Sweden's consequent abandonment of the Kalmar Union, and continued with the reign of Gustav's sons Eric XIV, John III, John's son Sigismund, and finally Gustav's youngest son Charles IX.
Relevant evidence: Yes