Date: 19th century to date
The root cause of the Arab–Israeli conflict is the territorial dispute between Israel and mostly Islamic Palestine. In the late 19th century, a wave of Zionism spread across Jewish communities in Europe seeking to return to God’s promised land and establish a Jewish state. Nevertheless, at the time, the promised land was already populated by Palestinians who were mostly Muslims. After 1890, Jewish migrants continued to flow into Palestinian settlements, chipping away the Palestinian residential area from 94% of the territory to less than 40% now. Palestinians have no place to go and live under constant oppression inflicted by Israel, many of whom have ended up in refugee camps as their territory continues to shrink. Hence the territorial dispute.
Another root cause of Israeli-Palestinian conflict is sovereignty over Jerusalem. Judaism, Christianity and Islam have all enshrined Jerusalem as their holy city and the three refuse to relinquish their sovereignty over the land. Religious conflicts on top of the loss of the Islamic territory of Palestine have triggered many wars in the Middle East between Islamic Arab countries and Jewish Israel.