On Tuesday, President Obama picked up the phone and talked to Cuban President Raul Castro.

The call came a day before Obama publicly announced the decision to normalize diplomatic relations between the two foes. Just how surprising would a call of that sort be? Remember, it was just a year ago that Obama and Castro shook hands at Nelson Mandela's funeral. That handshake unleashed a torrent of speculation about what it could mean.

We now know that Tuesday's phone call was the final piece of a negotiation puzzle that will result in the opening of a full-fledged diplomatic mission in Havana. That will mark the first time the U.S. will have an ambassador in the country since the U.S. broke off diplomatic relations in 1961.

If you remember, Obama made a similar, historic phone call back in September 2013. Obama had called Iranian President Hassan Rouhani. That talk was the first time the heads of states of the two countries had spoken directly since 1979.

In a lot of ways, these phone calls complete several promises Obama made during the 2008 campaign.

During a debate in July 2007,Obama was asked if he would be open to meeting with the leaders of Iran and Cuba "to bridge the gap that divides our countries?"

Obama said he would. He was careful to elucidate.

"And the reason is this, that the notion that somehow not talking to countries is punishment to them — which has been the guiding diplomatic principle of this administration — is ridiculous," Obama said.

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