John Kerry was angry.

“Listen to this. Listen to what Trump just said about John McCain,” Kerry was saying over the phone. “‘He’s not a war hero. He’s a war hero because he was captured. I like people who weren’t captured.’

“That’s unbelievable,” Kerry said. “That’s beyond outrageous.’”

“John and I have some serious differences on a lot of things but he is nothing other than a hero and a good man. Where was Trump when John got shot down over North Vietnam? In school? At a party? Where was he?”

For many months now, years even, Kerry has been point man in Barack Obama’s attempt to restrict Iran’s plan to develop a nuclear bomb. He has been a walking high-wire act, traveling a region that is nothing less than a geographical bonfire filled with the debris of failed nations, countries that have collapsed into chaos and terror largely because of the contrived plans of men like Dick Cheney who dreamed of the day when Saddam Hussein could be toppled. The conservative ideologues got their wish while the United States got a larger, longer war and the Middle East became an even bigger source of horror and death.

Trump’s assault on McCain evoked immediate anger in Kerry because it resurrected feelings within him that are always there, certainly beneath a surface calm but always, always there: a long gone war called Vietnam.

“All of us sat for weeks and months around a table trying to get this deal done,” Kerry was saying. “The Russians, the Chinese, the French, the British, the Germans, all of us. And every once in awhile I thought about that other table, that other time, and that was nearly a half century ago.”

He was talking about the Paris Peace Talks that began in 1970 and concluded with an agreement signed on January 23, 1973. Henry Kissinger represented another president, Richard Nixon. John McCain was in Hanoi, in captivity. John Kerry had returned from Vietnam to help organize Vietnam Veterans Against The War. Donald Trump was somewhere else.

As talks in Paris dragged on, more than half of the 58,195 names carved into the wall of the Vietnam Memorial in Washington were killed. Thousands more were wounded and carry those wounds still, today.

Both Kerry and Obama are firm believers that conversation is a better starter-kit than combat when it comes to dealing with a country like Iran. Neither man is naive about that nation’s aspiration to dominate the region.

“But the Iranians are not suicidal,” Kerry pointed out.

Clearly, the Iranians are well aware that Teheran would be turned into a field of glass and sand if they ever stepped toward open war with Israel or Saudi Arabia. And every nation around that table in Vienna knew that the sanctions that crippled the Iranian economy and caused Iran to accept a deal would soon collapse under the weight of countries like France, Russia and China that were eager to begin doing business in Teheran, the dollar emerging as the strongest weapon of all.

So as he shuttled back and forth between Washington and Vienna, his leg broken, his spirit determined, Kerry found himself thinking about that other time and those other talks. He is a student of history and in his mind’s eye he saw another president, Lyndon Johnson, broken by a long war that still lingers in the American psyche. He thought about the Ivy League sophisticates that surrounded John F. Kennedy and then Johnson, men named Bundy, Rostow, McNamara, and others who spent the lives of so many younger men pursuing their old men’s dreams of defeating communism in the lethal laboratory of Vietnam.

In a trick of history and irony communism collapsed on a deathbed that Ronald Reagan helped make up by…talking; talking to Mikhail Gorbachev. A wall fell. One continent, Europe, changed forever. Two nations, Russia and the United States, altered their behavior toward each another because of a handshake and a conversation.

Last week, John Kerry returned to the United States. After months of discussion, Germany, China, France, the United Kingdom, and Putin’s Russia along with the U.S. had a deal with Iran. Now it goes to a Congress more than half full of politicians who place a higher priority in defeating anything Barack Obama supports than educating the country and the world with an honest debate about a deal structured to insert more than a decade’s worth of roadblocks in Iran’s drive to develop a nuclear weapon.

And as John Kerry came home, his mind filled with facts, the ups, the downs, the potential, and the politics of getting an accord with Iran through the Congress, he was brought back to his own war five decades ago. A war that won’t go away. A war that awoke him one more time because of a libelous slur uttered by a real estate man against a friend of Kerry’s who will line up against him on the treaty with Iran. But that didn’t matter because brothers in arms form a bond far stronger than politics.