In 1042, Vladimir Yaroslavich, presumably together with his father, made a successful campaign against the Yem tribes that inhabited the territory of modern Southern Finland. Chronicles describe this campaign very sparingly.
It is known that the Kyiv troops defeated the enemy, captured prisoners and valuable booty, but on the way back there was a big loss of horses.
In the year 6550 (1042). Vladimir, the son of Yaroslav, went to Yam and defeated them. And the horses of the Vladimir warriors died, and if the horse was still breathing, they skinned it: there were many deaths among the horses. – The Tale of Bygone Yearswikipedia