horses were widely kept in semi-feral conditions through the mid-19th century. Ethnologist Kustaa Vilkuna describes how all horses regardless of sex and age were let out on forest pastures for the summer after the spring fieldwork was finished. The pasture was scarce and the terrain challenging, with both rocky ground and wetlands. Vilkuna considers this practice an important factor in making the Finnhorse an easy-keeping, hardy breed. Military use The goal of Gustav Vasa and others had been to increase the height of the Finnish horse. However, the Finnish cavalry survey records (katselmuspöytäkirjat) from the 1620s indicate this goal was not achieved. The heights of horses surveyed in 1623, measured not at the withers but at the highest point of the croup, which provides a height measurement significantly different from standard measures, ranged between , the taller animals being the horses of officers. Only the horses owned by Colonel Herman Fleming were taller, with a croup measurement of . It is not known if these horses were domestic crossbreeds or imported. The average height of the horses of the troops of Hollola, Pori and Raseborg was only one year, but those in the next year's survey were . Overall, there were no pony-sized horses below a croup measurement of , and the all-around average height of the horses used by the cavalry was about . During the Thirty Years' War in 1618–1648, the horses used by Finnish cavalry were small and unrepresentative, considered inferior even to the cargo horses used by the Swedish Royal Army. However, these animals had great stamina, a crucial quality during long, exhausting campaigns. The humble-looking Finnish horses were presumably exchanged when possible for other horses obtained as spoils of war. It was probably rare for a cavalryman to return with the same horse with which he left, and it is likely that the horses brought back to Finland were crossbreeds or of purely Central European lines. Reinforcements to replace the considerable horse casualties were obtained from the Baltic States, but during the reign of Charles XI almost all of the cavalry horses were imported from south of the Gulf of Finland, due to their larger size. Before World War II, the Finnhorse was the breed that made up almost all of the horses that were part of the Finnish army and mounted police forces. While officers mostly rode various foreign light horse breeds, the so-called