After a couple of years of truce, in 1654 the Cossacks allied with the Russian tsar in the Treaty of Pereyaslav which led to the Russo-Polish War (1654-1667), besides the Second Northern War (1655–60) with the invasion from Sweden. These wars led to a period of mass murders and poverty known as the Deluge. The Russian army from North, and the Cossacks from South, occupied the territories of the Greek-Catholic Church, and destroyed churches, monasteries, and schools, and killing priests and monks.