Rerum Moscoviticarum Commentarii

Notes on Muscovite Affairs (Rerum Moscoviticarum Commentarii) (1549) was a Latin book by Baron Sigismund von Herberstein on the geography, history and customs of Muscovy (the 16th century Russian state). The book was the main early source of knowledge about Russia in Western Europe.

Herberstein was an Austrian diplomat who was twice sent to Russia as Austrian ambassador, in 1517 and 1526. Born in Vipava (German Wippach), Slovenia, he was familiar with Slovene, a Slavic language, which became important later on his mission in Russia, when he was able to communicate with ordinary Russians in Slovene, another Slavic language.

These visits occurred at a time when very little was known about Russia outside the region. The few published descriptions of Russia were in some cases wildly inaccurate.

Muscovy in the 16th century was the Russian state which separated itself from the Kievan Rus' after it fell apart. It evolved into the Russian Empire under Peter the Great starting at the end of the 17th century. Russia was the region, Muscovy was the state until it no longer included just Moscow. Muscovy was then ruled by the Muscovite monarchy, starting with Ivan III (1462–1505), who expanded Muscovy, and ending with Ivan IV, who claimed the title "Tsar of Russia".

In this article, Russia and Muscovy are treated as similar entities. In land area there is not much difference between Muscovy and Russia west of the Ural Mountains. Herberstein wrote about Muscovy (region based on Moscow) because that is what it was known as in the West then. We know the area as Russia, so that is how it is referred to here.

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