[1] On 25 September, Gert von Rantzau learned of the planned operation, allegedly from observing the Swedish ships in Skäggenäs, and thus led three companies of infantry from his own regiment, under Valentin Rosworm, Christopher Luppert, and Jørgen Baroldt respectively across the strait to Öland.

Later on the same day, in the evening of 26[1] or 27[2] September, Gustavus Adolphus crossed the Kalmar Strait, landing near Stora Rör, 18 kilometers south from Borgholm.

When Rantzau attempted to return to the mainland by sea in order to bring reinforcements, his yacht was swept eastwards to Gotland because of unfavourable winds, delaying the response.

[6][1] Most of the German soldiers in the Danish companies enlisted in the Swedish army, while Adolphus sent the others to Kalmar, after they had swore to not fight Sweden for three months.

[7] Hammarskiöld received the three Swedish cavalry banners and four infantry companies to defend the island, and the peasant representatives who crossed the strait in order to swear fealty to Christian IV were put on trial and later executed for treason.