Why is part of the island of Ireland part of the UK?

Before Ireland became independent, the island of Ireland had always been part of the United Kingdom. After Ireland became independent, it had a complicated issue with the United Kingdom over the ownership of Northern Ireland.

The island of Ireland is a small area. As the homeland of Ireland, the Irish have always wanted to take back Northern Ireland. Because Ireland is weak and Britain refuses to give in on the Irish issue, the Irish have never been able to take back Northern Ireland as they wished.

In order to gain independence for Northern Ireland, the Irish formed an independent army and used various radical methods such as terrorist attacks and riots to deal with the British in the hope of gaining independence. The British are still very tough on the Northern Ireland issue. They bluntly say that Northern Ireland is British territory and refuse to return it.

Extended information:

Most residents of Ireland are of British descent. Since they are a minority on the island of Ireland, and they are incompatible with the Irish in terms of religion, culture, and lifestyle, they have always been in opposition to the Irish. They have always been loyal to the United Kingdom and firmly stand on the British side.

Ireland is the earliest British colony. Britain has huge interests in Ireland, and Ireland has special significance to Britain. The island of Ireland is the British base on the island of Ireland, the basis of British control and influence on Ireland, and a symbol of the dignity of the British Empire.