It is massively complex , and I certainly don't pretend to understand it all.
But the outline information I have ( I am not on one side or the other ) mainly from movies and documentaries:
British Empire 'owned' or rather ruled over the area of Palestine.
Zionists and other denominations of jews had been in the area for some time, and Britain agreed to give them a portion of the area of Palestine. People were hugely anti-semitic, and they wanted the security of having their own space.
Of course, historically the Jewish people did come from this part of the world but were expelled: like Biblical times.
BUT the land was given without the permission of the people living there and around it: agreements were drawn and re-drawn.
WW2 happened, the holocaust etc, and of course the Jewish people more than ever wanted their own state and many fled to Israel.
So the agreement with Britain was on shaky ground. Britain buggered off and left them to it: or rather the UN took responsibility for refereeing.
Then peoples homes were demolished, people were killed on both sides, everyone staking claim to the same bits of land.
LOTS of shit went down.
The in the 70s the Munich massacre (this is where my movie knowledge comes from: see 'Munich') confirmed an 'eye for an eye' approach by Israel, seeing as the international community carried on with their Olympics despite the massacre of the Israeli team: pah to them, we will get revenge, we won't take it lying down etc.
Lots more shit went down, and Israel helped with the massacre of people in the Lebanese war (See the film 'Waltz with Bashir' - VERY good on Israeli guilt and echoes of the holocaust).
Lots and lots more shit: all in a terrible tangle.
SORRY if this offends: I am very very ignorant of all of this, but seem to be confronted by people on all sides taking a black and white view. MY only view is that this is a real shitter and I'm just not sure how it will be solved.
I know this subject is like incendiary, in more ways than one.