Israel was created by United Nations vote, and was done so without the support of any of the Arab states. So they felt the decision was illegal to begin with. The Arab countries and the Palestinian Arabs believed the land of Palestine had been wrongly occupied by the British, wasn't theirs or the world's to give away, and now was illegally occupied by the Israelis.
Once Israel received its independence in 1948, the Arab countries felt that, worse than being colonized, now the holy land had fallen into the hands of non-believers, infidels, and for good unless they acted. So they attacked militarily to attempt to destroy Israel immediately.
In order to look at the entire picture of the conflict over Israel, one would have to look at the relationship between the Jews and the Muslims. The conflict has existed since the earliest of civilizations. When the people of Israel moved into the territory it was occupied by the Palestinians. They were suddenly bombarded with the Jewish culture, faith, and language. The presence of the Jews in the area had been established for over 3,300 years.
Great Britian began to recognize that Israel belonged to the Jewish people, but was concerned what to do about the Palestinian people who already occupied the area. The state was divided into two states, Israel and the other half stayed an Arab state. In 1948 the state of Israel was established with the agreement of the United Nations.
The Arab countries were not in agreement and the following countries, Egypt, Syria, Transjordan, Lebanon and Iraq, invaded Israel. (1948 War of Independence) They wanted to remove the newly established State of Israel and give it back to the rule of the Arab people. In addition, the Holy land of Jerusalem was also a place of honor for several significant religions in the world.
The War for Independence continues and the following other wars happened after the first attempt to take Israel down; 1956 Sinai War, 1967 Six Day War, and the 1973 Yom Kippur War.
The people of Israel believe that the land was promised to them by their God and the Arabs believe that the land is their own Holy place.