Jaromar acted in support of Jakob Erlandsen, Archbishop of Lund, in his conflict with Danish King Christoffer I.

King Christoffer had strongly resisted the archbishop’s efforts of adjusting the legislation and juridical right of the Danish church with canonical law.

After an incarceration of the Bishop, Jaromar ravaged Zealand during 1259 and broke through Copenhagen's fortifications in the place where Jarmers Tower was later built.

Wends warriors destroyed the city by burning down most of the houses and ended up by demolishing the castle of Bishop Absalon on Slotsholmen.

Between 1880-1885 the rampart area around Jarmers Tower was excavated and the moat leveled in connection with the Nordic Exhibition of 1888.