Here is some history about Gaza, to show for how long this occupation state is deliberately committing its war crimes.

From an article with the title:"The Ordeals of Gaza"

"Israeli military spokesmen, justifying their army's assault on the Gaza Strip, said the war was about Sderot. In a way, they were right. It is about Sderot. In 1948, where Sderot houses Israeli Jews today, there was a village called Najd - Arabic for a high plateau. It was home to about seven hundred people, most of them small farmers. Two days before the declaration of the State of Israel - that is, on May 13th - Haganah forces expelled the inhabitants.
Eventually, these people - as the Egyptian Army that invaded Palestine a few days later gradually lost ground to the new Israeli Army - found refuge in the Gaza Strip....
The Middle East Department of Israel's new foreign ministry made clear what fate was intended for them. Again, I quote from Tom Segev's 1949:
The department staff estimated that the refugees would "manage." As they put it, "the most adaptable and best survivors would manage by a process of natural selection, and the others will waste away. Some will die but most will turn into human debris and social outcasts and probably join the poorest classes in the Arab countries." Ben-Gurion informed the Minister for Immigration, Moshe Shapira, that the "Government line is that they may not return. That was in April 1949. (page 30)" Link: charlesglass.net/archives/2009/01/the_ordeals_of.html

And as Moshe Dayan stated in an oration at the funeral of an Israeli farmer killed by a Palestinian Arab in April 1956:

". . . Let us not today fling accusation at the murderers. What cause have we to complain about their fierce hatred to us? For eight years now, they sit in their refugee camps in Gaza, and before their eyes we turn into our homestead the land and villages in which they and their forefathers have lived. We should demand his blood not from the [Palestinian] Arabs of Gaza but from ourselves. . . . Let us make our reckoning today. We are a generation of settlers, and without the steel helmet and gun barrel, we shall not be able to plant a tree or build a house. . . . Let us not be afraid to see the hatred that accompanies and consumes the lives of hundreds of thousands of [Palestinian] Arabs who sit all around us and wait for the moment when their hands will be able to reach our blood." (Iron Wall, p. 101)"

And regarding Hamas, just go and find out about the role of the Mosad and Golda!

“Thanks to the Mossad, Israel’s “Institute for Intelligence and Special Tasks”, the Hamas was allowed to reinforce its presence in the occupied territories. Meanwhile, Arafat’s Fatah Movement for National Liberation as well as the Palestinian Left were subjected to the most brutal form of repression and intimidation
Let us not forget that it was Israel, which in fact created Hamas. According to Zeev Sternell, historian at the Hebrew University of Jerusalem, “Israel thought that it was a smart ploy to push the Islamists against the Palestinian Liberation Organisation (PLO)”.
Ahmed Yassin, the spiritual leader of the Islamist movement in Palestine, returning from Cairo in the seventies, established an Islamic charity association. Prime Minister Golda Meir, saw this as a an opportunity to counterbalance the rise of Arafat’s Fatah movement. .According to the Israeli weekly Koteret Rashit (October 1987), “The Islamic associations as well as the university had been supported and encouraged by the Israeli military authority” in charge of the (civilian) administration of the West Bank and Gaza. “They [the Islamic associations and the university] were authorized to receive money payments from abroad.”…” For full article and details here is the link:
globalresearch.ca/articles/ZER403A.html