There have been plenty of examples on the world stage of duos that thrived, but few had the personal and political connection that was shared by former British Prime Minister Margaret Thatcher and President Ronald Reagan, experts say.
The conservative icons met prior to becoming leaders of their respective countries and formed a personal relation built on their shared politics. And it's a bond that carried them through the tough times they faced as leaders, joined in promoting conservatism domestically and eliminating communism globally.
"When the Iron Lady vouched for [Mikhail] Gorbachev's authenticity, it carried a weight that no one else on the world scene had," says Richard Norton Smith, a presidential historian at George Mason University. "I'm not saying Reagan would not have developed the relationship he did, but I have to believe that her endorsement helped to facilitate that relationship."
Nancy Reagan called her husband and Thatcher "political soul mates."
"It is well-known that my husband and Lady Thatcher enjoyed a very special relationship as leaders of their respective countries during one of the most difficult and pivotal periods in modern history," she said in a release. "Ronnie and Margaret were political soul mates, committed to freedom and resolved to end communism."
But the two differed when it came to personality and politicking, says Allan Lichtman, a history professor at American University.
"Ronald Reagan was one of the most personable politicians we've ever had in the United States, he was the master of the one-liner, he was extraordinarily good at disarming his opposition – Margaret Thatcher didn't have those kinds of personal skills," Lichtman says. "She tended to be the kind of politician who worked more with fierce determination and iron will rather than charm and personality."
And there were also times of disagreement – like when Reagan authorized an invasion of Grenada, at that time officially under British control, without letting Thatcher know first.
"These are two politicians with their own objectives for what they were trying to do in the world, they didn't always agree," says James Cooper, a historian currently at the Churchill Institute at Westminster College and author of "Margaret Thatcher and Ronald Reagan: A Very Political Special Relationship."
More often than not, however, Thatcher and Reagan united to further their political goals, such as bringing about an end to the Cold War or promoting conservative economic principles.
Cooper says they were also willing to use the other to provide political cover.
"Thatcher could say, 'the economic changes I'm bringing about, they have legitimacy because Ronald Reagan is going to do them' and Ronald Reagan could say, 'I'm doing the same thing Margaret Thatcher is doing,'" he says. "Often they didn't agree, but they were able to come back together because they were very close friends."
Lichtman says the power of the two was incalculable, both at home and abroad.
"Together they changed the whole political conversation in both of their nations," he says. "They both had lasting impacts on their nations and the world in this conservative transformation of the late 1980s."