After the Americans and their allies won the Revolutionary War against the British in 1783, relations between the two nations were abysmal. But today, the United States and the United Kingdom have a "special relationship."

So when, exactly, did the trans-Atlantic cousins become friends after all that tea was dumped in the water? Pretty quickly, experts say, even if it wasn't until much later that the relationship achieved the geopolitical importance it enjoys today.

"America started off as a power aligned with France," said David Dunn, a professor of international politics at the University of Birmingham in the U.K. That's no surprise, given that France fought alongside the American revolutionaries to oust the British from the rebelling 13 colonies. In fact, France's participation in the Revolutionary War is, in large part, why France went broke and later had a revolution of its own to oust its king and queen.

But then, the French Revolution took an unexpected turn, and French and American relations soured. "The terror that followed the French Revolution and the executions of so many aristocrats was seen as debauched by people back in the United States," Dunn told Live Science.

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That view pushed the U.S. into a neutral stance when it came to the centuries-old rivalry between France and the U.K., opening a chance for America to patch things up with the British. This opportunity suited many Americans, who had a lot in common with the British.

"The U.S. essentially had an English legal system in its foundation," Dunn said. "The English language is another dominant factor. Large amounts of immigration from the U.K. to the U.S. continued after independence, and so did trade. You also had this long-standing fashion, where rich American heiresses married poor-but-noble-born Brits. Winston Churchill is the product of one such marriage."

Given these similarities and cultural exchanges, the U.S. and the U.K. were natural bedfellows.

This relationship faced another test during the War of 1812, when British forces captured Washington D.C., and set fire to much of it. "The low point for the relationship was the burning of the White House in 1814," said Tim Oliver, a senior lecturer in the Institute for Diplomacy and International Governance at Loughborough University London. "Over the course of the 19th century, relations improved, in part because of the business opportunities the USA started to offer."

But tensions did simmer beneath the surface of an otherwise-friendly accord during the following century. The main issue of contention was the British system of imperial preference, whereby trade within its empire was largely tariff-free. The U.S. resented having to pay levies on importing and exporting to the lucrative markets within the British Empire, such as India.

"The Americans didn't like that, and so wanted to dismantle the empire — and they did this by calling it 'undemocratic' and 'unrepublican,' which, obviously, you can argue it was," Dunn said. "But it was also about breaking up what they saw as the monopoly of the British Empire. This was really a feature in the 19th century and into the 20th."

Despite these pressures, diplomatic relations remained cordial, and the partnership developed into a truly meaningful and collaborative alliance during World War II. In one case, Prime Minister Winston Churchill overstayed his welcome at the White House during the Christmas of 1941, much to First Lady Eleanor Roosevelt's chagrin, but it ended up becoming a landmark moment in trans-Atlantic relations. President Franklin D. Roosevelt and Churchill often stayed up late into the night, plotting their war strategy while quaffing booze and smoking cigars.

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"There are a couple of funny stories that come out of that stay," Dunn said. "Churchill came out of the bath without his robe, and somehow, FDR came across him and was startled. Churchill said, 'The prime minister of the United Kingdom has nothing to hide from the president of the United States.' It was an extraordinarily close relationship."

The chumminess, while genuine, was also a product of necessity. The U.K. and its empire had been fighting a global war alone for over a year after the French surrendered and before the attack on Pearl Harbor forced the U.S. into the fray. The British were desperate for help. The U.S., meanwhile, was grateful to find a war-hardened and strategically located ally willing to host its troops for the fight against Germany. The relationship also resonated beyond the level of president and prime minister, Oliver said, and that was important in making the alliance close.

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"At the top, you had a combined strategic thinking and planning — [U.S. Gen. Dwight] Eisenhower and [U.K. Field Marshal] Alan Brooke — who set the tone and direction beneath the close political relationship of Churchill and Roosevelt," Oliver told Live Science. "Further down, you had the shared sacrifices and operations of the military in almost every major theater of war."

After the war, Churchill was voted out of office, and he decided to go on a speaking tour of the U.S. That's when Churchill coined the term "special relationship" — and it stuck. The intelligence sharing and military collaboration between the two countries endured throughout the Cold War, and the U.K. and U.S. have invariably seen many of their interests aligned ever since.

Originally published on Live Science.