With the assistance of the Arabs the British in 1917-18 took Palestine from the Turks near the end of WW1 The Arabs assisted the British because they were led to understand they would be independent at the end of hostilities. Unfortunately the British had also made promises to the Jews and the two promises were not compatible.
The Balfour Declaration of the 2nd of November 1917 was originally a letter sent from the British Foreign Secretary, Arthur James Balfour to Edmond J Rothchild, a prominent British Jew and Zionist supporter. The letter stated the British Governments support for ' the establishment in Palestine of a national home for the Jewish people.
2nd November 1917
Dear Lord Rothschild:
I have much pleasure in conveying to you on behalf of His Majesty's Government the following declaration of our sympathy with Jewish Zionist aspirations which has been submitted to, and approved by, the Cabinet. 'His Majesty's Government view with favour the establishment in Palestine of a National Home for the Jewish people, and will use their best endeavours to facilitate the achievement of this object, it being clearly understood that nothing shall be done which may prejudice the civil and religious rights of existing non-Jewish communities in Palestine, or the rights and political status enjoyed by Jews in any other country.' I should be grateful if you would bring this declaration to the knowledge of the Zionist Federation.
Arthur James Balfour
In 1920 Britain was granted a mandate over Palestine. Palestine was divided into Palestine and Transjordan in 1921 and the Kingdom of Jordan was created by treaty in 1923. With the Balfour declaration, Britain's aim was to win the support of Jews for the Allied cause in WW1. On the 24th of July 1922 the Declaration was incorporated into the League of Nations Mandate for Palestine which enumerated the terms under which Britain was given responsibility for temporary administration of the country on behalf of the Jews and Arabs living there.
The mandate lasted from 1922 to 1948, during which time the British found themselves, because of their contradictory promises, in a most difficult and finally untenable situation, but one of their own making. On one hand, the Zionists anticipated large numbers of Jews immigrating to Palestine and a new Jewish state was anticipated. On the other hand, the Palestinians feared the loss of their land to the Zionists and feeling let down by the British, were reluctant to listen to further promises made by them.
Despite the back and forth policy of the British, first supporting one side then the other, Jewish immigration did increase. In 1935 approx. 60,000 Jews moved into Palestine. In 1936 An Arab revolt broke out based on the fear that outsiders were going to take over their country. There were intermittent attacks on various Jewish settlements until 1939. By that date the British had managed to contain the Jewish immigrants, and the struggle for Palestine abated during WW2.
After the war, the struggle resumed and although Britain refused to admit 100,000 Jewish survivors of the Nazi death camps, large numbers gained entry by illegal means. In 1947 Britain declared the mandate unworkable and passed the problem over to the United Nations. On 14th May 1948 The United Nations announced plans to partition Palestine into separate Jewish and Arab states at the end of the British mandate in Palestine on the 27th of June.
This led to an increase in the Arab conflict with the Jews due to the reduction of British forces, which were being gradually concentrated around Haifa to keep this port open for the final evacuation. Violence increased, murder and sabotage of British personnel and equipment increased. The Royal Marines among other forces were deployed in the troubled areas to try and keep the peace until the British withdrawal was completed.