UN created after World War 2 (1945) where their aims to achieve the world peace within the countries because world has been witnessed too many war. In UN around 193 countries joined UN. All the countries joined UN because thay want to be protected by UN. In World War 1, about 9 000 000 people died because of the nature and more than 20 000 000 people was injured. Britain was the bigger empire and they want the world peace and they establish the Lead of Nations.
There are differences between UN and Lead of nation. Their aims are the same but UN is a big organization while Lead of nation is not an organization like UN. UN with the different nations are together and also it have universal declaration of human right where nation have to be treated equally and human right is for all people regardless the race, nationality, people and region.
In World War 2, more than 20 000 000 people were died. This war is bigger than World War 1 and it is desire to make sure the peace of the world. While World War 2 happened, the bomb was released in Nagasaki and Hiroshima. The condition of the place was extremely worse, and now Hiroshima recovered but still has a remnant of the war. UN had become one of the organization who creating among the countries who joined UN.