The Agency's SIGINT history can be traced back to the establishment of Finnish radio intelligence in 1927 by Reino Hallamaa, a Defence Command intelligence officer, while its GEOINT history starts from 1812 with the establishment of the Haapaniemi military surveying school and topographical service. The successes of its predecessors are considered instrumental in key battles of the Winter and Continuation War during 1939–1944, such as intelligence at the largest battle in the history of Nordic countries, the Battle of Tali-Ihantala.