Gustaf Eriksson Vasa enters history as one of the hostages sent King Christian by Sten Sture in October 1518. The king stowed the hostages, renounced his truce with Sture, and returned to Copenhagen. From Copenhagen young Vasa was taken to Kalø and held by his kinsman, Erik Banner. At the end of the next summer, the hostage escaped and headed south, disguised, according to some accounts, as a drover. The fugitive arrived in Lübeck September 30, 1519, and sought refuge with men involved in trade with Sweden, Kort Koninck, Hermann Iserhel, and Marcus Helmstede, Sten Sture's factor in Lübeck.

Magistrates granted the young Swede asylum in return for a promise not to leave the city before the next Easter. When Banner arrived in pursuit of the fugitive, the town council refused to hand him over; he had been taken to Denmark unjustly, and had never promised to stay put. Young Vasa used his stay in the city to acquaint himself with Lübeck's relations with other Hanse towns and the tensions with Denmark and the Netherlands. From afar he followed the downward spiral of events in Sweden, the Danish invasion in 1520, and the death of Sten Sture.

On May 13, 1520, Lübeck agreed with Duke Friedrich at Segeberg to suspend trade with Sweden until Easter the next year. That agreement may have triggered Gustaf Vasa's departure. He took passage on the smack Korpen, and landed at Stensö, south of Kalmar, May 31, 1520.