Pereyaslav Articles

The Pereyaslav Articles (Переяславські статті, Переяславские статьи) were concluded on October 27, 1659 between Yuri Khmelnytsky, the son of Bohdan Khmelnytsky, and the Russian tsar. The treaty drastically limited the Ukrainian (Cossack) autonomy. This second treaty was an aftermath of the Treaty of Hadiach from 16 September 1658 between the Cossacks and the Polish-Lithuanian Commonwealth, which granted many privileges to Cossacks and thus threatened Russian influence over Cossacks. The articles imposed severe restrictions on Cossack Hetmanate autonomy.

The treaty
Under the new articles, Ukraine was not allowed to conduct any foreign policy including military alliances. The Cossacks were not allowed to declare war without the approval of the tsar.

Under the treaty, Muscovite military governors and garrisons were placed in Bratslav, Chernihiv, Nizhyn, Pereiaslav, and Uman (previously they had only been in Kiev since 1654). Ukrainian Cossack forces were also withdrawn from Belarus. In addition, the Cossacks could no longer elect their own hetmans or colonels without the approval of the tsar.

Aftermath
The most significant immediate consequence of the Accords was the separation of the Ukrainian Orthodox church from the Patriarch of Constantinople and its subordination  to the Patriarch of Moscow. The treaty led to popular unrest and later influenced Khmelnytsky's decision to ally with Poland in 1660.