On 28 April 1724, the city of Emden called on its possession Oldersum to prepare for war and arm themselves. On 2 February 1726, troops from Emden fought a battle in Leer against the princely troops. The latter were victorious. Soon afterwards, the renitent faction was condemned in an imperial decree. The conflict, however, continued and on 7 April 1726, another battle was fought in the streets of Leer, killing and wounding many soldiers. In April 1727, the Prince called in reinforcements from Denmark. A group of 60 men from Oldersum united with troops from Emden and other localities in the Emden area and marched to Norden, where they lost another battle against the Prince's army. Another imperial decree again condemned the renitent faction and ordern them to pay reparations. The Prince took over the administration of Oldersum from the city of Emden, and imperial troops occupied the castle at Oldersum. When the conflict ended, the Prince emerged victoriously and the recalcitrant city of Emden had to submit to him. However, the Prince had won a Pyrrhic victory.
Question: The city of Emden called on its possession Oldersum how many years before the Prince called in reinforcements from Denmark to help with the bettle?
Answer: 3