 On 7 June 1238, by the Treaty of Stensby, the Teutonic knights returned the Duchy of Estonia to Valdemar II, until in 1346, after St. George's Night Uprising, the lands were sold back to the order and became part of the Ordensstaat.After the conquest, all of the remaining local population were ostensibly Christianized.In 1535, the first extant native language book was printed, a Lutheran catechism.