Directors Ken Burns and Lynn Novick said on CBS News' "Face the Nation" that during the Vietnam War, there was a "sea of change" from when the war began to when it ended, particularly as it related to America's leaders.

The duo's new documentary series, "The Vietnam War," which charts the buildup to the war during the 1960s and the fallout thereafter, provides insight on the discord that developed between the American people and the presidency.

"There was a sense that we believed in our leaders, that they were -- good people, that they knew what they were doing, that they were competent, that they would do what was in the best interest of the nation, that they would not lie to the people. They would tell the truth, you know, and that they would sort of carry on the nation's business in the best possible way," said Novick.

Novick says that idea of trust started to quickly erode as the U.S. was fully engaged in Vietnam.

"You had sort of a credibility gap, where the public began to doubt that they were getting the true story under Johnson. And it sort of metastasized into terrible cynicism under Nixon that we cannot trust our presidents, that they don't tell us the truth, that they are not doing the right thing, and that, you know, just sort of a pox on both their houses," added Novick.

Burns added that the film also explores both the humanity and failure of the role of the presidency during the contentious time period.

"You're perceiving this momentum that all of them know exactly that this is not going to work out, that as you know we have a strategy of not losing rather than winning or any articulation of particular goals that would represent winning. And then they're also saying one thing in public and another in private," said Burns.

Novick and Burns also note the stark parallels between the American presidency in the 1960s and today in their latest series.

"It's become sort of from naïve idealist sort of faith to skepticism to cynicism. And that's a disturbing thing," said Novick.

She added, "you hear this in the audiotapes that we were able to include in the film where you hear our presidents speaking privately, especially Johnson and Nixon, about what they really think about the war, which is they have terrible doubts. They have no confidence. They want to get out. They don't see the point. And they go out on television the next day and say, 'Everything's going great.'"

Burns' and Novick's ten-part, 18-hour documentary film series premieres on PBS Sunday, September 17, at 8 p.m. ET.