Which two of the following were main causes of arab israeli conflict in the twentieth century

Two main causes of Arab Israel conflicts in the twentieth century were:
The first one is the division of Palestine into separate Jewish and Arab states. 
This general articulation is very known, as every one of the three monotheistic religions guarantee responsibility for Holy Land. 
We can for the most part say that after the Crusades, Christians stayed out of the contention because of the monstrous misfortunes they confronted when they had endeavored to attack and vanquish it (when Salah Al deen was at influence, before the ascent of the Ottoman domain).
The second one would be, US support for Israels military
The US is a nearby partner of Israel, and this is essentially why there are enormous issues and clashes between the two religions whom are living in a similar region/land.