There are several and I'm pointing a few below. I'll recommend you these two books which are pretty reliable if you're looking to develop a balanced PoV. Modern history of Palestine is a quite polemic subject and has a tendency to draw emotionally-charged discussions.
Righteous Victims: a History of the Zionist-Arab Conflict, 1881-1999 (Benny Morris)
The First Ten Years: a Diplomatic History of Israel (Walter Eytan)

• Following WW1, you are aware Palestine was ceeded from the Ottoman Empire to Britain as a time-limited Mandate territory within the League of Nations framework. It wasn't supposed to last forever;
• Following WW2, there was a huge Ashkenazi (European) Jew influx towards Palestine motivated by the Holocaust, and this has increased the already existing tensions between the Jewish and Arab communities living under British administration;
• There were clashes between these two groups and, in 1947, the situation escalated. British forces in the region, which were supposed to enforce order, were being targeted by terrorist groups, especially underground Jewish organizations such as the Irgun;
• Britain has announced in November 1947 (check the UN Resolution 181) its will to terminate the Mandate as it was unable to commit more resources to the region. The Empire's power was already receeding and this process would reach its apex after only 8 years when the Suez Canal (which was jointly administered with France) is completely nationalized by Nasser/Egypt.

Overall, call it pressure. There was pressure coming from every direction. Internally, Britain's scarce post-WW2 resources were being drained and this leveraged political dissent. From around Palestine, Transjordan (aka Jordan) had recently been granted independence by Britain and the Arab world saw this as a precedent for Palestinian Arabs. From within Palestine, there was a violent Zionist and Arab uprising escalating into civil war as Britain gradually took its troops from the land.