Hillary and Henry: Clinton's Relationship With Kissinger

Clinton and Kissinger's ties extend beyond politics.

The two former secretaries of state have been close for years, with Clinton calling him "a friend" and noting that she "relied on his counsel" when she was secretary of state from 2009 to 2013.

"He checked in with me regularly, sharing astute observations about foreign leaders and sending me written reports on his travels. Though we have often seen the world and some of our challenges quite differently, and advocated different responses now and in the past...." she wrote in a review of his book "World Order" that was published in the Washington Post in 2014.

She also included mentions of Kissinger in her own book "Hard Choices," which detailed her time as secretary of state, referencing him during portions about China.

Though she has not spoken at length about her relationship with Kissinger during her ongoing presidential campaign, Clinton hasn't shied away from her connection to the controversial Republican either.

During a debate in New Hampshire in February, Clinton brought him up as a positive.

Sen. Bernie Sanders has criticized her ties to Kissinger, saying during a subsequent debate that he found it "rather amazing" that she is proud of the connection "because I happen to believe that Henry Kissinger was one of the most destructive secretaries of state in the modern history of this country."