What caused the start of the iran irag war

Iraq invaded Iran in 20 September of 1980 which cause an eight year war. hope this helps.

The league of nations was found in 1919 to keep peace after world war l.but it failed to prevent world war ll in 1939,so in 1945 the nations of the world set up a new organization,the united state (un).since then, the un has encouraged international cooperation and worked to resolve conflict