According to one hypothesis, the tribe of Sosols mentioned in Old East Slavic chronicles implies the people of Sakala.

The chronicles say that Kievan Rus organized military campaign against Sosols in 1060 and taxed them.

A year later, Sosols rose, destroyed Kievan Rus Fort in Tartu and tried to attack Pskov.

In Sackalian folklore, the neighbouring Ugaunians (ugalased) were enemy warriors and robbers.

For instance, a folk song from Viljandi, the capital of Sackalia, calls for speeding up the harvest work because the Ugaunians might attack.