WASHINGTON — The arc of Antony J. Blinken’s first year as secretary of state could be broken down into two distinct eras: before and after Afghanistan.

Before Afghanistan — before the Taliban seized control of the capital in August, forcing the closure of the U.S. Embassy and the chaotic evacuation of more than 124,000 people — Mr. Blinken’s efforts to restore American leadership in the world appeared to be paying off.

Allies welcomed the renewed attention after feeling mistreated during the Trump years. A burst of shuttle diplomacy helped quell an 11-day war between Israel and Hamas. Even a heated public debate with Chinese envoys became a moment for the new secretary of state to highlight the Biden administration’s top foreign policy priority.

But on the morning of Aug. 15, Mr. Blinken looked ashen on Sunday news shows as he defended President Biden’s decision to leave Afghanistan, and how the departure unfolded.

“This is heart-wrenching stuff,” Mr. Blinken said on CNN, noting reports of renewed Taliban threats to Afghan women and girls.

Current and former State Department officials, and foreign diplomats, say Mr. Blinken has spent the months since then trying to recover.

It has not been easy.

Though he leaves on Monday for Australia and Fiji to continue rallying allies against China, Mr. Blinken has most recently been focused on heading off the latest global crisis — a possible Russian military invasion of Ukraine. In scores of meetings and phone calls with foreign leaders, he has tried to help craft a unified response against a familiar adversary. But it remains to be seen whether he can recast the administration as a reliable partner with a reasoned strategy as he enters his second year in office.

The exit from Afghanistan “was a pivot point, perhaps, for people to recognize how broken everything was, and therefore, almost how impossible it was going to be for Biden to really be able to turn everything around to some romanticized pre-Trump era,” said Barbara K. Bodine, a former U.S. ambassador to Yemen and a 30-year veteran of the Foreign Service who is now the director of the Institute for the Study of Diplomacy at Georgetown University.

“It was a gut check on reality,” she said.

Experts said Mr. Blinken would also need to resist being pulled so deeply into any given disaster, on any given day, that he is diverted from longer-term policy priorities that he has said will resonate for years to come: curbing the pandemic and global warming, setting international standards for using technology and leveling the playing field for American workers.

Close to the President

Unfailingly polite and even-keeled, Mr. Blinken is a studiously careful speaker who stays relentlessly faithful to talking points. But he also has a lighter side, occasionally indulging cornball jokes and puns.

He began working for Mr. Biden in the Senate in 2002, and remains the first among equals among the president’s security advisers.

“If you are speaking to Tony Blinken, you’re essentially speaking as directly as you can to President Biden with him not being there,” said Thomas E. Donilon, whom Mr. Blinken succeeded as the White House deputy national security adviser during the Obama administration.

Mr. Blinken remains anonymous enough that he can slip into an outdoor Parisian cafe, as he did this spring, without causing a ruckus — a sharp contrast to the dominating presence that most of his immediate predecessors used to bring a sheen to American diplomacy.

Condoleezza Rice attracted special attention as the first African American woman to hold the job. Hillary Clinton’s foreign travels drew crowds eager for a glimpse or a photo with her. John F. Kerry was an instantly recognizable political celebrity and a former Democratic presidential nominee. And Mike Pompeo carried himself like a military commander — not just of American diplomats but also of allies and adversaries.

Mr. Blinken has instead tried to portray himself as a quiet peacemaker.

During a visit last month to Kyiv, the Ukrainian capital, Mr. Blinken assured the government and the public that “the United States stands with you resolutely in your right to make decisions for your own future, to shape that future as Ukrainians for Ukraine.”

President Volodymyr Zelensky of Ukraine said Mr. Blinken’s visit underscored “the strong support for Ukraine’s independence and sovereignty from the United States.” Senator Rob Portman, Republican of Ohio, who had recently visited Kyiv as part of a congressional delegation, told Fox News that “I was very pleased to see those strong words from Secretary Blinken.”

Hours later in Washington, Mr. Biden suggested that the United States might “end up having a fight” with European allies about how to respond if Russia ordered a “minor incursion” into Ukraine. That did not sit well with Mr. Zelensky.

“We want to remind the great powers that there are no minor incursions and small nations,” Ukraine’s president said on Twitter. “Just as there are no minor casualties and little grief from the loss of loved ones.”

Mr. Blinken spent the next several days talking to allies — including Ukraine’s foreign minister — to reaffirm “unwavering support for Ukraine’s sovereignty and territorial integrity,” said his spokesman, Ned Price.

Representative Gregory W. Meeks, Democrat of New York and the chairman of the House Foreign Affairs Committee, said Mr. Blinken’s core principles were evident in his efforts to resolve the Ukraine crisis: defending democracy, building international alliances, and deploying sanctions and other tools against adversaries instead of military force.

“What the department is doing now is explaining more than ever what diplomacy is and how diplomacy is as effective, and can be less expensive, than military options — that we have to exercise and pursue diplomacy with everything that we have, as opposed to putting the military options in the front burner,” Mr. Meeks said in an interview, before leading another congressional delegation to Kyiv.

The dialogue has turned more coercive in recent days, with the Biden administration ordering 3,000 additional troops to Eastern Europe as U.S. and Ukrainian officials say roughly 130,000 Russian troops have massed on Ukraine’s borders. But Mr. Blinken has said he would continue to push “a serious diplomatic path forward, should Russia choose it.”

After Kabul

A peaceful resolution would also give Mr. Blinken an opportunity to polish over the lackluster last months of 2021.

In October, he had to answer to furious French officials about a submarine deal with Australia and Britain that left Paris — one of Washington’s oldest allies — in the cold.

The reset with China — an endeavor loosely defined as a competition, a collaboration and a confrontation — has yielded mixed success. Climate talks in Glasgow in November ended with an agreement to curb emissions. But China continues to needle the Biden administration by buzzing Taiwan with warplanes, hacking into software used in sensitive computer systems worldwide, outspending the United States in foreign infrastructure investments and pledging to send more coronavirus vaccines abroad than any other country.

Negotiations to revive the 2015 Iran nuclear deal, which President Donald J. Trump abandoned, until recently appeared all but over.

At the State Department, as many as 90 senior jobs remained vacant at the start of January, according to the U.S. Global Leadership Coalition, as both the White House and the Senate stalled on advancing candidates.

Over it all hung a cloud of low morale and coronavirus malaise at the department that during the Trump administration had stunted diplomats’ muscle memory by the time Mr. Blinken took over just a little over one year ago.

Mr. Blinken’s professional devotion to Mr. Biden comes at a cost. Some current and former diplomats privately said they wanted to see a more visionary foreign policy.

“Things are not pulled together,” Ms. Bodine said. “When you don’t really have a strong vision or an overall strategic view, then you are more susceptible to being diverted.”

Senior State Department officials disagree, and say Mr. Blinken has sought to show that the most urgent issues of diplomacy are matters that have a direct effect on Americans. Central to that strategy was managing the U.S. relationship with China, which he called “the biggest geopolitical test of the 21st century.”

Mr. Blinken began and ended his official travels during 2021 in Asia to showcase what working with the United States could offer.

“We all have a stake in ensuring that the world’s most dynamic region is free from coercion and accessible to all,” he said in Jakarta, Indonesia, in December.

While there, Mr. Blinken said the Biden administration had donated more than 25 million doses of Covid-19 vaccine to Indonesia, compared with three million donated by China. Most of the vaccines that China has designated for Indonesia have been sold for profit — about 250 million doses so far.

In another example, department officials noted that the Biden administration swooped in to assist Lithuania, through the U.S. Export-Import Bank, after China launched a trade war against the tiny Baltic country.

The assistance has been welcomed, by both smaller nations that were caught between the United States and China during the Trump administration, and close allies who described a strain with Washington before Mr. Biden was elected.

“It’s much more easy now, because we share so many more of our values and the things we would like to do together,” Foreign Minister Ann Linde of Sweden said in January at a forum hosted by the Center for American Progress. “So for me, it’s kind of a relief.”

Yet many allies fear it will all be overturned if U.S. voters choose a new government in 2024 that echoes the Trump administration’s “America First” ideas. That is one reason the Iran nuclear negotiations have struggled, given Tehran’s wariness of reviving a deal that another administration might again terminate.

And the chaotic departure from Afghanistan did little to ease concerns about American reliability.

Barbara J. Stephenson, another former American ambassador who is now the vice provost for global affairs at the University of North Carolina at Chapel Hill, called the disjointed evacuation “a huge disrupter” for the State Department. She said it demonstrated to adversaries like President Vladimir V. Putin of Russia and President Xi Jinping of China “the value of distracting us.”

It even angered Americans who supported Mr. Biden’s decision to end the war.

“We defended him,” said Dan Caldwell, the vice president for foreign policy for Stand Together, an advocacy group funded by the conservative billionaire Charles Koch. “But that was always done under the belief that later on, there needed to be accountability. And now five months later, you’re still seeing issues with evacuations.”

“That is just unacceptable,” he said.

Mr. Blinken has said not only that he was surprised by the retreat of President Ashraf Ghani and Afghan security forces as the Taliban advanced last August, but that “we inherited a deadline — we did not inherit a plan” when he took over the department.

He has appointed a career diplomat, Dan Smith, to lead a fact-finding mission into the chaotic evacuation, including why the State Department did not begin issuing visas earlier in the Biden administration to tens of thousands of Afghans who had worked for the United States during the war.

Congress has also demanded an explanation for how senior officials underestimated the threat to the U.S. Embassy in Kabul that ultimately led to its closure. Already, officials said, the State Department has more aggressively assessed whether to close embassies in Addis Ababa, Ethiopia, and Kyiv in the face of approaching conflict.

“We knew this would be challenging,” Mr. Blinken said in December of the withdrawal from Afghanistan. “It was.”