John Kerry has done it again. Against the odds and confounding all expectations, the top US diplomat has pulled off a second major arms deal with a recalcitrant state in a matter of months.
After marathon Geneva talks, Kerry emerged with an interim deal with Iran to roll back its nuclear program which for years has eluded the global community.
It comes just weeks after a September accord brokered with Russia to eliminate Syria's declared chemical arms -- even though Damascus had refused previously to openly acknowledge that it even possessed such a toxic arsenal.
It's a huge coup for the former long-time senator who took over as secretary of state from Hillary Clinton in February, and who, in a nod to his reputation for being slightly dull, joked then that he had "big heels to fill."
But as he prepares to mark his 70th birthday next month, Kerry can be forgiven for showing some satisfaction at his first 10 months in office, and a record which has won him grudging respect from the White House.
"Agreement in Geneva: first step makes world safer. More work now. -JK #IranTalks," Kerry wrote on the State Department Twitter account.
In the months since he took charge of some 70,000 diplomats and the bureau known by its Washington location as Foggy Bottom, Kerry has waded unflinchingly into the world's most intractable problems.
Even his quixotic quest to try to resolve the 60-year-old Israeli-Palestinian conflict bore fruit when he doggedly pushed the two sides back to the table after a three-year hiatus, though a deal remains a long way off.
Clinton, who always had an eye on her image and a potential 2016 White House bid, steered clear of getting bogged down in the messy diplomacy required in the Middle East.
But if Clinton was the right woman at the start of President Barack Obama's tenure to restore America's tattered reputation overseas, perhaps Kerry is the man for a second-term Obama aiming to carve out a legacy on foreign policy.
Armed with seemingly endless patience, a love of his own voice and a bountiful dose of self-confidence which fuels his belief in his powers of persuasion, Kerry has proved a tireless negotiator.
"Kerry is a difference maker," Joel Rubin, director of policy for the Ploughshares Fund, told AFP, also praising the "limitless energy" of Kerry's team.
"He seems to be the type of secretary who wants to roll up his sleeves and get into the weeds, and is willing to burn the midnight oil. That builds confidence in the parties."
Kerry's staff talk of seeing him going through the Syria chemical weapons deal line by line, pencil in hand, along with his Russian counterpart Sergei Lavrov.
He has spent hours locked in rooms with Israeli Prime Minister Benjamin Netanyahu in his seven trips so far to Israel and the West Bank.
He stayed longer than planned in Kabul in October to hammer out a bilateral security deal with the notoriously mercurial President Hamid Karzai, which is now being debated by the traditional assembly or loya jirga.
Yet he is also known for veering off script, and more than once his press people have been forced to walk back verbal gaffes that have left White House officials shaking their heads.
Although Kerry claims that he deliberately floated the idea of Syrian President Bashar al-Assad turning over his chemical weapons, most observers believe he actually misspoke at a London press conference and the idea was seized on by Lavrov, who laid down the gauntlet to the White House.
His ranks of senior advisors are also worryingly thin, and some diplomats have privately complained that little policy direction is trickling down from the top.
Analyst Aaron David Miller, who worked for six secretaries of state, has described Kerry as "the Energizer bunny" of American diplomacy.
While all the ingredients may be present for Kerry to become a truly consequential secretary of state, Miller has words of caution.
"You take a lot of heat for being naive, overextended, too eager for the deal. And there's always the risk of being taken for granted," he wrote in Foreign Policy magazine.
"A secretary must maintain a certain amount of detachment, creating the mystique of being unavailable and inaccessible. It creates authority."