Judaism
Christianity was originally a sect of Second Temple Judaism, but the two religions diverged in the first century. The differences between Christianity and Judaism originally centered on whether Jesus was the Jewish Messiah but eventually became irreconcilable. Major differences between the two faiths include the nature of the Messiah, of atonement and sin, the status of God's commandments to Israel, and perhaps most significantly of the nature of God himself. Due to these differences, Judaism traditionally regards Christianity as Shituf or worship of the God of Israel which is not monotheistic. Christianity has traditionally regarded Judaism as obsolete with the invention of Christianity and Jews as a people replaced by the Church, though a Christian belief in dual-covenant theology emerged as a phenomenon following Christian reflection on how their theology influenced the Nazi Holocaust.
Religious anti-Zionism
Today, the main Jewish theological opposition to Zionism stems from the Satmar Hasidim, which has more than 150,000 adherents worldwide. Even more strongly opposed to Zionism is the small Haredi Jewish organization known as Neturei Karta., which has less than 5,000 members, almost all of whom live in Israel and Palestine. According to "The Guardian", "[e]ven among Charedi, or ultra-Orthodox circles, the Neturei Karta are regarded as a wild fringe".)