After being treated to a rare inspection of China's first and only aircraft carrier, the US defence secretary heard sharp words from his Chinese counterpart on Taiwan and Japan - a spicy exchange that broke from the traditional bland pronouncements of previous such visits.
As the first Vietnam war veteran to have run the Pentagon and a vocal opponent of the war in Iraq, Hagel knows the importance of exhausting diplomatic options before resorting to military action. His 10-day trip proved to be no small test of his skills and resolve to do so.
The shift of focus from the strife-torn Middle East to Asia was apparent in Hagel's visit, which analysts saw as paving the way for US President Barack Obama's tour of the region this month.
The US administration is seeking to pull off an almost impossible balancing act: reassuring countries in the region that the United States' "pivot" to Asia, a policy long seen in China as a move to contain its rise, is proceeding while at the same time seeking military co-operation with Beijing.
And while Hagel's public exchanges with the Chinese top brass were unusually frank, analysts said the straight-talking maverick had taken a big step towards preventing military miscalculation, with its potential to escalate into conflict, by engaging in a more direct and honest discussion of the two countries' differences and clashes of interest.
"Sweeping our differences under the rug and pretending they don't exist is not only unwise but dangerous," said Bonnie Glaser, a senior adviser for Asia at the Centre for Strategic and International Studies based in Washington DC.
"It's important to engage and narrow differences on where we can and where we can't to ensure we don't have miscalculation on various issues."
Despite US military budget cuts, Hagel spared no effort during his trip to tell East Asian nations the region remains a priority for Washington and that the US will not shy away from confronting China.
In Japan, he urged China to respect its neighbours and drew a direct comparison between Russia's annexation of Ukraine's Crimea region and the territorial dispute between Beijing and Tokyo over islands in the East China Sea.
Stressing the importance of US "treaty obligations" to American allies, he told US and Japanese forces at Yokota air base, was one of the goals of his trip. "We are serious about that," he said.
But Washington says it takes no position on the sovereignty of the islands, called the Senkakus by Japan and the Diaoyus by China, although it recognises Tokyo's right to administer them.
US officials have publicly stated that the islands are covered by the US Japan security treaty, a point Hagel also stressed during his meetings in Beijing.
Some in Japan fear its biggest ally may not be able or willing to come to its defence in the event of military conflict over the islands.
During his meeting with Chinese defence minister Chang Wanquan in Beijing, Hagel reiterated US objections to China's air-defence identification zone over the disputed sea. The declaration of the air zone in November was condemned in the region, as it came without consultation and many see its overlap with Japan and South Korea's air defence zones as confrontational.
Equally worried are the Southeast Asian nations contesting claims with China to islands in the South China Sea. At a three-day meeting in Hawaii, the first stop on his trip, Hagel told his counterparts in the Association of Southeast Asian Nations that the US was increasingly concerned about instability in the South China Sea.
Although he did not mention China by name, Hagel said all countries concerned should make their cases based on international law, an indirect reference to China's vaguely defined claim to about 90 per cent of the sea. Other claimants, and more recently the US, have questioned if that claim is consistent with international law.
In a rare public rebuttal, Chinese leaders made sure their discontent was heard.
"The Chinese people, including myself, are dissatisfied with such remarks," Fan Changlong , a deputy chairman of the powerful Central Military Commission, told Hagel at a meeting, referring to his statements in Japan and Hawaii.
Chang made it known that the Chinese armed forces were "ready to assemble at the first call" and were "capable of winning". The US should "stay vigilant" over Japan, he added.
Chang also urged Washington to block a Congressional bill that reaffirms the US commitment to Taiwan and calls for continued arms sales to the island.
Both sides describe the exchanges as candid and constructive. And the trip was not without positive signs. Hagel became the first foreign leader to get aboard the Chinese aircraft carrier, a potent symbol of the country's rising military might. The two militaries also pledged to enhance co-operation. Communication lines will be set up to establish a notification mechanism for navy and air-force activities at sea in an effort to avoid the risk of miscalculation.
Being more honest could help to prevent miscalculation, but some Chinese observers warn that structural problems and fundamental mistrust remain major hurdles.
"It's a good thing the two countries are talking things out, but this will not change the course that will see a rising nation clashing with the existing hegemony," said Ni Lexiong , director of a defence policy centre at the Shanghai University of Political Science and Law.
Hagel's visit also had its lighter moments.
The former radio-show host made some off-the-cuff comments during a lunch at an officers' school in Beijing.
"Is that a hotdog?" the 67-year-old asked, pointing to a sausage on the lunch plate of a young soldier sitting next to him at the school's canteen.
"You are still growing, I am not," he told the young man as he savoured his kung pao and dumplings.
In his last stop, in Mongolia, Hagel was given a horse as a gift by his counterpart, Bat-Erdene Dashdemberel, which he opted to leave behind.
"You be good while I am gone," Hagel told the horse, which he named Shamrock.
In Ulan Bator, Hagel thanked Mongolia for sending troops to Iraq and Afghanistan. While serving as a Republican senator, Hagel drew criticism from his own party for his strident opposition to the war in Iraq. A recipient of two Purple Hearts, one for saving his brother, his nomination as Pentagon chief was opposed by some in his own party.
Although his appointment came only after a nomination stalled in the Senate by an unprecedented filibuster, and a confirmation margin of 58 votes to 41 that was the lowest for any successful cabinet nominee since 2007, some consider Hagel a fitting figure to run the Defence Department as the US looks set to push for a speedier withdrawal of its forces from Afghanistan.
More substantive measures were expected to be announced during Obama's visit to back up the rhetoric of reassurance, said Robert Sutter, a professor of international affairs at George Washington University in Washington.
Bonnie Glaser's name was misspelled in a previous version of this article, which also erroneously identified her as being based in Jakarta. It should be Washington DC.