Idaho senator that led the irreconcilables?

Answer:
It was led by Idaho Senator William Borah.
The irreconcilables opposed the 'Treaty of Versailles' of 1919 at the end of World War I.
The irreconcilables consisted of about 12 - 16 Senators (both Democrat and Republicans) who opposed the treaty. They succeeded and the United States never ratified the 'Treaty of Versailles' and the United States never joined the 'League of Nations'.
First answer by ID1193450965. Last edit by Tasmanianman. Contributor trust: 31 [recommend contributor recommended]. Question popularity: 1 [recommend question].