The crusaders set off
19. September 1217
In the morning of September 19 the latest, crusader's army set off. They used the old war road, passing through Ruhja and Karksi, and moving towards Viljandi.
On the morning of September 20, the army came to the areas near Halliste and Karksi, where some troops were sent ahead to scout.
Germans received information about the size of the Estonia army and about their movement from nearby villages. The knowledge that the inhabitants of Saccalia's southern parishes had about the Estonian army about 30-40 km northwards, shows that Saccalian elders had implemented a very effective messenger network all over their county.
On September 19 the latest, also the Estonians had set off, after they had waited for 15 days for the Russians to arrive. Perhaps the reason to move on was to go meet the Russians on half way, to find out about the crusader's army, or perhaps to go raid Livonia on their own.
It must be kept in mind that back then it was quite complicated to supply a large army staying put for a long time, hence perhaps another reason to move was that it was impossible to camp at that location any longer.
By the eve of September 20, the crusaders, who were alert and moving on slowly, reached Viljandi, where they spent the night. In the following morning, on Saint Matthew's Day, mass was held; then the army moved on towards the camp site of the Estonians. Germans found out that the latter had moved to South-West instead, to Pärsti-Vanamõisa region. Germans followed.
Source: Sulev Vahtre. Muinasaja loojang Eestis: vabadusvõitlus 1208-1227. Tallinn: Olion. 1990
Evald Tõnisson, Jüri Selirand ja Artur Vassar. Kui Lembitu kutsus... Tallinn: Eesti Raamat, 1968
Image source: http://esttrip2008.files.wordpress.com/2008/02/viljandi.jpg