Under the Marxist-Leninist doctrine of state atheism in the Soviet Union, after its foundation in 1917, Christmas celebrations—along with other religious holidays—were prohibited as a result of the Soviet anti-religious campaign. The League of Militant Atheists encouraged school pupils to campaign against Christmas traditions, among them being the Christmas tree, as well as other Christian holidays, including Easter; the League established an anti-religious holiday to be the 31st of each month as a replacement. With the Christmas tree being prohibited in accordance with Soviet anti-religious legislation, people supplanted the former Christmas custom with New Year's trees. In 1935, the tree was brought back as New Year tree and became a secular, not a religious holiday.