Who is Israel?

Who is Israel?

Theologians argue about who 'Israel' is. It is the name given by God to Jacob. But it also refers to his children as the Sons of Israel who were brought into Egypt by Joseph when he was King of kings. Then the nation of Israel split into Two nations: Israel and Judah. After the captivity, the returning people were known as Israel. Some also call the church Israel. In 70 A.D. Jerusalem was destroyed and the nation ceased to exist. In the last century, the Rothchilds took possession of the land of Israel from the British in payment for war debts, and a new nation was formed.

A man, several nations, and a church are all called Israel. How do you know when it means one or the other? Is a promise made to the man valid for the nation, nations or the church? Are commands given to the nation, but not to the man, valid for the church?

Surely God must have given us a way to know which Israel is which and how to apply his word.