Explanation: Basically, all of those groups claim all of Jerusalem as a holy city (Christians because its where Jesus did most of his work, the Jews because its the major city in the historic area of Judea, also known as the Holy Land, and Palestine, where Moses lead the Israelites to have a safe place away from enslavement, (as well as having several major temples and synagogues and the Muslims because its one of the three cities Mohammad went to in his pilgrimage across Arabia, the other two being Mecca and Medina and having the third holiest site in the religion, the Al-Aqsa Mosque) But the British, in an effort to prevent violence between the three groups, separated them. However, because all three claim it all, they want it all. So militant groups of the three religions take it upon themselves to take it "back" for their religion (truth be told, all three major religions have at one point or another held the area, the Crusader States, the Islamic Caliphates, and the independent state of Judea before the Romans came and went) Many also believe that Israel is oppressing Arab Palestinian Muslims and Christians, but that gets into some pretty controversial territory. Over time though, there have been several wars, such as the Six Day War, where Israel successfully defended itself against literally all of its neighbours, as well as terrorism from the Arab Palestinian Muslims.