How Israel was formed?

After world war one the British managed to take control over parts that were previously owned by the Ottoman empire. The British conquered Syria as a result. (See Summary of the Syrian Crisis)

Zionism , a political movement of Jews that supports the re-establishment of a Jewish homeland, emerged in the late 19th century.

After the war the Balfour Declaration , which was issued by England, promised Jewish people a homeland in the mandatory state of Palestine which was carved out of Syria. 

The Jews started migrating from all over the world to the mandatory state of Palestine. 

Tensions grew between Arabs and Jews which led to unrest in the area. The British suggested to divide the area into Jewish and Arab states. The proposal led to more tensions in the area.

As tensions grew further England raised the matter to the united nations. The united nations divided the land into Jewish and Arab states as per Resolution 181(II). (See Why the United States is called a nation of immigrants?)

In 1948 the Israeli states declared independence.

A massive migration of Jews occurred. According to Wikipedia 42% of all Jews are now located in Israel.

England recognized Israel as a nation then shortly Israel was given a seat in the united nations.