Split of early Christianity and Judaism in the context of "God in Christianity"

Christ, used by Christians as both a name and a title, unambiguously refers to Jesus. As a title it is used both in the reciprocal form "Christ Jesus", meaning "the Messiah Jesus" (or "Jesus the Khristós"; lit. "Jesus the Anointed"), and independently as "the Christ". The earliest texts of the New Testament, the Pauline epistles, often refer to Jesus as "Christ Jesus", or simply "Christ".

The concept of the Christ in Christianity originated from the concept of the messiah in Judaism. Christians believe that Jesus is the messiah foretold in the Hebrew Bible and the Christian Old Testament. Although the conceptions of the messiah in each religion are similar, for the most part they are distinct from one another due to the split of early Christianity and Judaism in the 1st century.

The persecution of Christians can be traced from the first century of the Christian era to the present day. Christian missionaries and converts to Christianity have both been targeted for persecution, sometimes to the point of being martyred for their faith, ever since the emergence of Christianity.

Early Christians were persecuted at the hands of both Jews, from whose religion Christianity arose, and the Romans who controlled many of the early centers of Christianity in the Roman Empire. Since the emergence of Christian states in Late Antiquity, Christians have also been persecuted by other Christians due to differences in doctrine which have been declared heretical. Early in the fourth century, the empire's official persecutions were ended by the Edict of Serdica in 311 and the practice of Christianity legalized by the Edict of Milan in 312. By the year 380, Christians had begun to persecute each other. The schisms of late antiquity and the Middle Ages – including the Rome–Constantinople schisms and the many Christological controversies – together with the later Protestant Reformation provoked severe conflicts between Christian denominations. During these conflicts, members of the various denominations frequently persecuted each other and engaged in sectarian violence.

The term Judeo-Christian is used to group Christianity and Judaism together, either in reference to Christianity's derivation from Judaism, Christianity's recognition of Jewish scripture to constitute the Old Testament of the Christian Bible, or values supposed to be shared by the two religions. The term Judæo Christian first appeared in the 19th century as a word for Jewish converts to Christianity. The term has received criticism, largely from Jewish thinkers, as relying on and perpetuating notions of supersessionism, as well as glossing over fundamental differences between Jewish and Christian thought, theology, culture and practice.

In the United States, the term was widely used during the Cold War in an attempt to invoke a unified American identity opposed to communism.

The persecution of Christians in the New Testament is an important part of the Early Christian narrative which depicts the early church as being persecuted for their heterodox beliefs by a Jewish establishment in the Roman province of Judea. The New Testament, especially the Gospel of John, has traditionally been interpreted as relating Christian accounts of the Pharisee rejection of Jesus and accusations of the Pharisee responsibility for his crucifixion. The Acts of the Apostles depicts instances of early Christian persecution by the Sanhedrin, the Jewish religious court.

Walter Laqueur argues that hostility between Christians and Jews grew over the generations. By the 4th century, John Chrysostom was arguing that the Pharisees alone, not the Romans, were responsible for the murder of Christ. However, according to Laqueur: "Absolving Pilate from guilt may have been connected with the missionary activities of early Christianity in Rome and the desire not to antagonize those they want to convert."

The history of the Jews in Greece can be traced back to at least the fourth century BCE. The oldest and the most characteristic Jewish group that has inhabited Greece are the Romaniotes, also known as "Greek Jews." The term "Greek Jew" is predominantly used for any Jew that lives in or originates from the modern region of Greece.

Aside from the Romaniotes, a distinct Jewish population that historically lived in communities throughout Greece and neighboring areas with large Greek populations, Greece had a large population of Sephardi Jews, and is a historical center of Sephardic life; the city of Salonica or Thessaloniki, in Greek Macedonia, was called the "Mother of Israel." Greek Jews played an important role in the early development of Christianity, and became a source of education and commerce for the Byzantine Empire and throughout the period of Ottoman Greece, until suffering devastation in the Holocaust after Greece was conquered and occupied by the Axis powers. Despite efforts by Greeks to protect them, some 4,000 Jews were deported from the Bulgarian occupation zone to the Treblinka extermination camp. In the aftermath of the Holocaust, a large percentage of the surviving community emigrated to Israel or the United States.

The circumcision controversy in early Christianity played an important role in Christian theology.

The circumcision of Jesus is celebrated as a feast day in the liturgical calendar of many Christian denominations, while the teachings of the Apostle Paul asserted that physical circumcision was unnecessary for the salvation of Gentiles and their membership in the New Covenant. The first Council of Jerusalem (c. 50) declared that circumcision was not necessary for new Gentile converts (as recorded in Acts 15); Pauline Christianity was instrumental in the split of early Christianity and Judaism and eventually became Christians' predominant position. Covenant theology largely views the Christian sacrament of baptism as fulfilling the Jewish practice of circumcision, as both serve as signs and seals of the covenant of grace.