President Barack Obama shakes hands with Cuban President Raul Castro during the official memorial service for former South African President Nelson Mandela at FNB Stadium, Dec. 10, 2013, in Johannesburg, South Africa.
camera (Chip Somodevilla/Getty Images) President Barack Obama shakes hands with Cuban President Raul Castro during the official memorial service for former South African President Nelson Mandela at FNB Stadium, Dec. 10, 2013, in Johannesburg, South Africa.

intro: President Obama caused a stir at the memorial service for Nelson Mandela by pausing to shake hands with Cuban President Raul Castro.

The United States has not had diplomatic relations with Cuba for over 50 years since the Communist revolution, led by the current president's brother, Fidel Castro.

The handshake at a memorial honoring the life and legacy of Mandela comes at a time when there have been glimpses of diplomatic reconciliation between the two countries.

But as history has shown, a handshake can indicate a momentous shift in geopolitics, or it can simply be a polite unavoidable gesture.

Here are some other headline-making handshakes between U.S. presidents and foreign frenemies:

quicklist: 1 title: Obama and Hugo Chavez text: Obama stirred up criticism early in his first term when he shook hands with Venezuela President Hugo Chavez at the Summit of Americas in April 2009.

Obama was said to have initiated the shake, and a photog snapped the two smiling. Chavez was quoted telling Obama "with this same hand I greeted Bush eight years ago. I want to be your friend," and gave him a copy of "Open Veins of Latin America," a 1971 book by Eduardo Galeano.

Many on the right were outraged by the friendly pandering, with Newt Gingrich saying on his Fox News show that the moment sent "a very sad signal about human rights around the world."

Obama later defended his actions, saying the U.S., "with its overwhelming military superiority and need to improve its global image, could afford to extend such diplomatic courtesy."

Relations with Venezuela never improved. media: 21166418

quicklist: 2 title: Obama and Vladimir Putin text: Making headlines not so much for the gesture as for its awkwardness was a snapshot of President Obama shaking Russia President Putin's hand at the G20 summit this past September.

With tensions brewing over Syria and Putin's recent grant of temporary asylum to Edward Snowden, it was all tight smiles as Putin greeted Obama in St. Petersburg. The brief encounter and body language was heavily dissected by news outlets, noting the "15-second" exchange.

Putin later said it wasn't about putting on a cheerful face.

"President Obama hasn't been elected by the American people in order to be pleasant to Russia," he told the press. "And your humble servant hasn't been elected by the people of Russia to be pleasant to someone either. We work. We argue about issues. We are human." media: 21166232

quicklist: 3 title: Obama and Moammar Gaddafi text: Soon after his well-publicized shake with Chavez, Obama made history as the first U.S president to shake the hand of Libyan leader Moammar Gaddafi.

Many saw the historic moment, occurring at a dinner held during the July 2009 G8 Summit in Italy, as a sign of improving relations between the U.S. and Libya as Obama continued to publicly reach out to controversial world leaders in attempts to improve foreign relations.

White House official Denis McDonough said at the time that it was never a question as to whether Obama would greet Gaddafi.

"He doesn't intend to choose which leaders he'll shake hands with and which he won't: he'll be very happy to greet everyone he meets."

Gaddafi was killed during Libya's 2011 revolution which was backed by U.S. air power. media: 21166050

quicklist: 4 title: Obama and King Abdullah of Saudi Arabia text: In 2009, while attending the London G-20 meeting, President Obama made a gesture that raised some eyebrows at home in the United States.

While meeting King Abdullah of Saudi Arabia, the president made a move that some people on the right interpreted as a bow.

The Obama administration denied that the president bowed to the Saudi Arabian king, and an aide told Politico, "It wasn't a bow. He grasped his hand with two hands, and he's taller than King Abdullah.

This would prove to be a gesture that would not go away for the president. In 2011, former presidential candidate Mitt Romney cited the event when he said Obama "has bowed to foreign dictators."

This wasn't the first interaction between a U.S. president and King Abdullah.

President George W. Bush had a 'close relationship' with the king. The two leaders had even been photographed walking hand and hand and sharing a kiss. The double kiss is a traditional gesture in the region. media: 21165974

quicklist: 5 title: Clinton and Hafez al-Assad text: In a foreign policy gamble, President Clinton made a stop in Geneva in 2000 to speak with Syrian President Hafez al-Assad.

The meeting was triumphed as an "epic" encounter by Syrian newspapers, and was a rare trip for the country's ailing leader.

The White House hoped that the meeting would create enough common ground for renewed talks between Israel and Syria, but according to a senior administration official, Assad was "immoveable" and "appeared to have come with the misconception that Mr. Clinton was in a position to give him what he wanted from Israel."

Hafez al-Assad died later that year and was succeeded by his son Bashir al-Assad. The U.S. is currently backing rebels in the Syrian civil war trying to overthrow the Assad regime. media: 21165882

quicklist: 6 title: Nixon and Mao Zedong text: It was a handshake for the history books.

Richard Nixon's handshake with Chinese communist leader Mao Zedong was one for the history books during the president's 1972 visit to the People's Republic of China--the first visit of it's kind by a U.S. president.

The shake, and visit, ended 25 years of separation between the two nations. The much-photographed image gave Americans glimpses of China for the first time in decades, and Nixon later dubbed the trip, "the week that changed the world." media: 21165689

quicklist: 7 title: Kennedy and Khrushchev text: President John F. Kennedy and first secretary of the Soviet Communist Party Nikita Khrushchev gamely shook hands for a photo op during the 1961 Vienna summit between the two world leaders.

But the shake hardly helped ease tensions thanks to the Soviet Union's successful space missions and the failed Bay of Pigs invasion of Cuba by U.S.-backed Cuban exiles.

The summit turned out to be brutal, with JFK later commenting the two-day summit was the "worst thing in my life," and that Khrushchev "savaged me."

The Cuban Missile Crisis and construction of the Berlin Wall happened mere months later. media: 21165297

quicklist: 8 title: Nixon And Fidel Castro text: Just four months after successfully leading a revolution in Cuba, Fidel Castro traveled to the United States for an 11 day visit in April 1959.

The visit came at a time when tensions were high between the two nations. In fact, Castro did not request, or accept, an official invitation for his visit to the United States. Instead, he came at the invitation of the American Society of Newspaper Editors.

President Eisenhower famously snubbed Castro on his visit to the U.S., but the new Cuban leader did meet with the next highest ranking U.S. leaders, Vice President Richard Nixon and Secretary of State Christian Herter.

After meeting with Castro, Nixon said he concluded that the Cuban dictator was "either incredibly naive about communism or under communist discipline. My guess is the former." media: 21165151