That is when Israel declared independence?
Were the Jews hungry for land and started kicking Arabs out, or did the Arabs attack first, or is it sort of a mixed bag?
In 1948, the Arabs attacked first. A few hours after Israel became an independent country, most of the Arab countries of the region invaded.
But that's just the 1948 answer.
Local Arab and Jewish militia forces had been clashing for years. A few months earlier (in 1947) bombings and shootings had increased to the level of a civil war. Jews were being driven out of their homes throughout the Arab world, then the Arabs were fleeing their homes in Israel during the '48 war. Whose fault it all was depends entirely on who you ask.
As the comments say you should separate Arab countries from local Palestinians.
We also need to decide on a date, since again like the comments mention a conflict existed between Jews and local Palestinians long before that. The end of the British Mandate in Palestine on 14 May 1948 marks the beginning of modern independent Israel.
Benny Morris and a group of Israeli historians wrote one of the most comprehensive books on this war called the birth of the Palestinian refugee problem containing a huge number of documents testimonies and interviews (and later the birth of the Palestinian refugee problem revisited with more declassified documents)
There is no free preview of the book, but here's some quotes from related articles:
From the moment the Yishuv [pre-1948 Jewish community in Palestine] was attacked by the Palestinians and afterward by the Arab states
the War of Establishment (milhemet hakomemiyut) -- was to have two distinct stages: a civil war, beginning on Nov. 30, 1947 and ending on May 14, 1948, and a conventional war, beginning when the armies of the surrounding Arab states invaded Palestine on May 15 and ending in 1949.
They argue about the consequences of the war or what did the Arab nations meant by attacking but Their conclusion about "who attacked first" seems simple- the Arabs nations.