Today, on Friday, September 19, Great Britain can breathe a huge sigh of relief. The people of Scotland voted Thursday to remain a part of the United Kingdom. This is great news not only for Britain, but also for the United States.  

The United Kingdom of Great Britain and Northern Ireland is America’s closest ally on the world stage. 

The Anglo-American "Special Relationship" is the engine of the free world, the most robust and enduring partnership of modern times. Anything that weakens that relationship is a negative for America. As the "Iron Lady," Margaret Thatcher, liked to say, America "needs friends in the lonely task of world leadership," and Americans have no better friends than their British allies across the Atlantic.

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Had Scotland opted for independence, Britain would have been thrown into turmoil. At a stroke, its population would have shrunk (following an 18 month transition period) by 5 million people and its land mass reduced by roughly a third.  

The financial markets in London would have gone into freefall, with the pound plummeting, and a cloud of economic uncertainty hanging over the world’s sixth largest economy. Undoubtedly, Wall Street would have taken a big hit too.

In addition the prime minister, David Cameron, would have faced a fight for his political survival, with a mounting rebellion within the ruling Conservative Party. The ensuing political instability in Westminster would have made it impossible for the British government to focus on the urgent task of fighting the ISIS menace in Iraq and Syria, throwing U.S. plans to build an international coalition against the Islamist threat into question. The last thing the United States needs as it goes to war against ISIS is its closest friend and partner at war with itself.

Thursday’s “no” vote also removes a massive headache that would have faced both British and U.S. defense chiefs. Britain’s nuclear deterrent is submarine-based, and entirely located in Scotland. 

If Scotland had opted for independence, London would have been forced to relocate its nuclear weapons, with no natural base in England or Wales. The Scottish nationalists had threatened to turn Scotland into a nuclear-free zone, a stance that goes against the spirit of the North Atlantic Treaty Organization, which is a nuclear alliance.

Americans should welcome the Scottish referendum result as a reaffirmation of a union that has existed for more than 300 years. It is a union that forged a mighty empire that gave birth to many of the world’s greatest democracies today, from the United States and Canada, to Australia and India. 

Scots have played a huge role in that history, as soldiers, sailors, airmen, explorers, economists, inventors and entrepreneurs. The fabric of Scotland’s rich and varied past is intricately interwoven with that of the rest of Great Britain. The British people can now look forward to a future with Scotland as an integral part, and this can only be good for America as well.

Nile Gardiner is Director of the Margaret Thatcher Center for Freedom at the Heritage Foundation and a former aide to Margaret Thatcher. Follow him on Twitter@NileGardiner.