According to the Russian Primary Chronicle, the town was the seat of Rurik's brother Truvor from 862-864.The next mention of the town in Slavonic chronicles dates back to 1233, when the place was captured by the Livonian Brothers of the Sword.In the later 1500s Izborsk was one of the smaller, but nonetheless strategically important fortresses that protected the northwest Russian borders from invasion. The fortress was supposed to be impregnable, which is why the seizure of it in 1569 by a small Lithuanian regiment came as such a shock to the then ruler, Ivan the Terrible.