Washington, Feb. 23 -- Over a century ago, the US Congress left Europe to its fate. It was the end of the First World War. The US, despite its initial reluctance, had joined the war and ensured a decisive victory for its allies against Germany. Woodrow Wilson had played a key role both during the war and in crafting a peace with the Treaty of Versailles. He put his weight behind the League of Nations, the precursor to the United Nations.

But the US Senate refused to ratify the Treaty, and with it, rejected the League and American participation in it. It remains one of history's big counter-factuals. If the Senate had let Wilson have his way, and if the US had joined the League, would there have been a Second World War?

One hundred and f...