Origins of Judaism
For centuries, the traditional understanding has been that Judaism came before Christianity and that Christianity separated from Judaism some time after the destruction of the Second Temple in 70 CE. Starting in the latter half of the 20th century, some scholars have begun to argue that the historical picture is quite a bit more complicated than that. In the 1st century, many Jewish sects existed in competition with each other, see Second Temple Judaism. The sects which eventually became Rabbinic Judaism and Early Christianity were but two of these. Some scholars have begun to propose a model which envisions a twin birth of Christianity and Judaism rather than a separation of the former from the latter. For example, Robert Goldenberg (2002) asserts that it is increasingly accepted among scholars that "at the end of the 1st century CE there were not yet two separate religions called "Judaism" and "Christianity"".
Daniel Boyarin (2002) proposes a revised understanding of the interactions between nascent Christianity and nascent Rabbinical Judaism in Late Antiquity which views the two religions as intensely and complexly intertwined throughout this period.
Hasidic Judaism
Outside pressure was mounting in the early 20th century. In 1912, many Hasidic leaders partook in the creation of the Agudas Israel party, a political instrument intended to safeguard what was now named Orthodox Judaism even in the relatively traditional East; the more hard-line dynasties, mainly Galician and Hungarian, opposed the Aguda as too lenient. Mass immigration to America, urbanization, World War I and the subsequent Russian Civil War uprooted the "shtetl"s in which the local Jews lived for centuries and were the bedrock of Hasidism. In the new Soviet Union, civil equality first achieved and a harsh repression of religion caused a rapid secularization. Few remaining Hasidim, especially of Chabad, continued to practice underground for decades. In the new states of the Interbellum era, the process was only somewhat slower. On the eve of World War II, strictly observant Jews were estimated to constitute no more than a third of the total Jewish population in Poland, the world's most Orthodox country. While the Rebbes still had a vast base of support, it was aging and declining.