Answer :

The United Kingdom was in control of Palestine from 1920 to 1948. This period is known as the British Mandate for Palestine.

Who and What:
This mandate was established by the League of Nations, an international organization formed after World War I, to administer the territories of the former Ottoman Empire that had been overrun by the Allied Powers.

When:
The British Mandate for Palestine officially began in 1920 following the end of World War I and the demise of Ottoman control. It continued until 1948 when the State of Israel was established.

Where:
Palestine is located in the Middle East, on the eastern coast of the Mediterranean Sea. During the period of the mandate, the area included modern-day Israel and the Palestinian territories.

Why:
The British were given control for several reasons. Primarily, during World War I, the British made conflicting promises regarding the future of Palestine, leading to complex diplomatic and political obligations. The Balfour Declaration of 1917, issued by the British government, expressed support for a "national home for the Jewish people" in Palestine while also pledging to protect the civil and religious rights of existing non-Jewish communities there.

Additionally, the British strategic interest in controlling Palestine included maintaining security of the Suez Canal, a crucial route for British naval and commercial interests.

How:
The League of Nations passed a mandate that legally transferred administrative control of Palestine to the British government. This mandate period saw significant political turmoil, with growing tensions between Jewish and Arab populations that eventually led to significant conflict.

In conclusion, the British control over Palestine was a consequence of post-World War I geopolitical arrangements and international diplomacy.