For 25 years, war has fortified — and nearly destroyed — the ties binding John McCain and John F. Kerry.

The two senators, who returned from Vietnam on opposite ends of the war and who split over Iraq, have in recent weeks come together to try to forge a new American foreign policy for the rapidly changing Arab world.

Concerned about what they consider an isolationist and fearful drift in both of their parties, Kerry (D-Mass.) and McCain (R-Ariz.) are advocating an even more forceful role for America in the world. Although the two men disagree on troop levels in Afghanistan, they see U.S. military might as necessary to maintaining world order and U.S. business investment as a key to reviving the economies of many Middle Eastern states.

Kerry and McCain are leading the fight in Congress to shore up support for U.S. action in Libya, trying to counter efforts by members of both parties to restrict activity there by introducing a resolution last week in support of the air campaign against Moammar Gaddafi’s regime.

The elder statesmen are also hoping to forge something resembling a Marshall Plan for the Middle East, aiming to spur massive private-sector investment across a region remade by revolution. The pair traveled to Egypt last weekend with eight Fortune 500 executives in an attempt to ignite investment in a country that has struggled since the February fall of longtime leader Hosni Mubarak.

In the twilight of their careers, Kerry and McCain have never held more sway. As chairman of the Senate Foreign Relations Committee, Kerry has become an adjunct member of President Obama’s national security team, parachuting into trouble spots to deliver messages to world leaders. McCain, the top Republican on the Senate Armed Services Committee, is the de facto GOP leader on all military matters.

The battle for Kerry and McCain now is to use their stature to convince war-weary lawmakers in both parties that the United States must take even more of a leading role in the world, not pull back from it.

So far, they have had limited success — the House rejected their Libya resolution in a bipartisan vote Friday. But the measure was approved Tuesday in Kerry’s Foreign Relations Committee on a bipartisan vote of 14 to 5 and now awaits action on the Senate floor.

The senators say they’ve seen tougher fights before.

“John and I are old warriors, old sailors, who have been down the same trails with different consequences,” Kerry, 67, said in an interview.

“We’ll succeed over time because events will prove us correct,” McCain, 74, said in an interview before his Middle East trip, which began Friday in Tunisia before meeting up with Kerry in Cairo.

Johnny and John Boy

Aside from policy, friends said they are relieved to see McCain and Kerry working together again, after a years-long feud driven by the Iraq war and their unfulfilled presidential ambitions. McCain now sometimes shows up unannounced in Kerry’s office to talk strategy. Kerry is fond of calling his old friend “Johnny,” while McCain tosses “John Boy” around, friends say.

At its core, the relationship is built on a shared belief in international engagement, what conservatives call “American exceptionalism” and what liberals refer to as promoting “American values.”

Either way, the Arab Spring pushed Kerry and McCain together. They have relished their role as agitators in chief, urging President Obama to embrace “the street” and distance the United States from dictators who had been longtime allies.

“It’s like two veterans on the opposite side of a conflict that’s now over,” said Sen. Lindsey O. Graham (R-S.C.), a good friend of McCain’s who has worked closely with Kerry. “After the heat of the battle, after the smoke has cleared, you tend to look back on your opponent with a different view.”

The first Kerry-McCain detente came 20 years ago, after a different Middle East war. Flying to Kuwait together after U.S. forces freed that nation from Saddam Hussein’s grip, they had their first heart-to-heart discussion about Vietnam.

Kerry won the Silver Star in February 1969 when, under enemy fire in the Mekong Delta, he ordered his patrol boat into the fight and attacked the enemy. He returned home and became an outspoken opponent of the war.

McCain became a hero for what he didn’t do. A naval aviator, his plane was shot down and he was held captive for 51 / 2 years, enduring brutal torture. The Vietnamese offered McCain, the son of a prominent admiral, the chance to leave. He refused. When he returned home, he stayed in the Navy and climbed its ranks before launching his political career.

Kerry won his Senate seat in 1984, followed by McCain two years later, and the men basically avoided each other. Working with Kerry would have been akin to accepting his 1971 testimony in which he mentioned “war crimes” committed by U.S. soldiers, according to McCain. “There was a distance between us,” he said.

That distance was bridged after the trip to Kuwait, and later that year Kerry became chairman of a Select Committee on POW/MIA Affairs. McCain and four other Vietnam veterans also served on the panel, spending several years working to normalize relations with Vietnam.

Politics and a split

But the Kerry-McCain partnership was derailed when Kerry won his party’s 2004 presidential nomination.

Kerry offered McCain the vice presidential spot. McCain’s camp says he repeatedly said no but the Democrat wouldn’t give up; Kerry’s camp says McCain considered the offer. After the proposal leaked to the news media, everyone became angry.

McCain said he couldn’t be part of an administration that would be dovish on Iraq. “It’s just that I felt that our philosophical differences meant that I could not serve,” he said in the interview.

When Kerry came under fire in the campaign from a group accusing him of inflating his military record, McCain spoke up for him. According to the Democrat’s friends, though, the Arizonan refused to allow his image to be used in ads defending Kerry.

“John and I went through a patch where we were on a different path,” Kerry recalled. “That doesn’t mean the friendship ended. We were sort of on hold.”

When McCain ran for president four years later, Kerry became a leading critic. He accused his old friend of ditching his principled stands to curry favor with conservatives. Some in McCain’s corner have never forgiven Kerry for accusing McCain of running a “fear and smear” campaign.

The two senators said last week that they have never spoken about their failed presidential campaigns. Asked today about the things that were done and said, neither man apologizes, neither offers regrets.

“I think I said some things that John found hurtful,” McCain said, unsure what those comments were. “Some things are said in campaigns that take awhile to get resolved.”

Kerry maintained that his critique was about policy. “That has nothing to do with the friendship,” he said.

‘Shared experiences’

Their friends say they began to realize just how oddly similar their lives and careers have been. They are the first senators since George McGovern (D-S.D.) in 1972 to win their party’s nomination, lose the general election and then return to the Senate.

“They have a lot of shared experiences. They both lost national elections. They both realized a productive life of service doesn’t end if you don’t win a national election,” said Sen. Joseph I. Lieberman (I-Conn.).

Appropriately, the most recent thaw in the Kerry-McCain relationship began at an event last July commemorating the 15th anniversary of normalizing relations with Vietnam. Both Kerry and McCain attended, and Kerry spoke in deeply personal terms about McCain’s “courage in captivity.”

Late last year, according to Graham, the Senate’s debate over the New START pact forced the duo to begin talking on a near-daily basis, including the time McCain and Graham showed up in Kerry’s office unannounced. McCain, according to aides, barked out to Kerry’s staff: “Tell John Kerry that there’s a crazy old right-winger in his front office waiting for him.”

McCain said the renewed partnership was driven by “a shared view of America’s role in the world,” with a touch of “shared misery” at each failed presidential bid. Most of all, he said, it came down to a basic decision: moving on, not quite forgiving but definitely trying to forget.

“I try very hard to put all these things behind me,” McCain said. “You’ve got to move on, and I will admit it: It took me a long time.”