 He was the operational planner whose collections of route maps and reports were used by Charles XII to prepare for the campaign in Poland and Russia.After the King's defeat in the Battle of Poltava (8 July 1709), Gyllenkrok followed the King to the Ottoman Empire, but was captured by the forces of Peter I of Russia at a mission in Poland.He was imprisoned in places such as Siberia, and did not return to Sweden until 1722.