The replacement theology, also known as supercessionism, is an interpretation of the Bible where the people of God are all seen as spiritual descendants of Abraham, such as described in Romans 4:11-12 and 9:6-8.
All who live by faith, just as he did before his circumcision, are part of the spiritual Israel. This interpretation eventually led to the application of all the unfulfilled promises about the nation of Israel to the followers of Jesus, both Jews and non-Jews.
Throughout the ages, the replacement theology has rooted deeply in the church, both in the West as well as in the Middle-East. It is probably because of this teaching that the Jews in Western-Europe have often been treated badly and at times even persecuted.