Outgoing U.S. Secretary of State John Kerry on Thursday afternoon told gathered staff that "we're living in a time of great transition and some upheaval."
In his final remarks at the State Department, however, Kerry added, "I am optimistic because this country has shown again and again how strong we are internally."
He waved goodbye in the C Street lobby, one day ahead of ending his tenure of just under four years as America's top diplomat.
WATCH: Kerry Excited about Next Chapter
Earlier Thursday, Kerry told State Department correspondents that he has traveled, as secretary of state, about 2,250,000 kilometers to 91 countries and spent 3,700 hours on the phone with world leaders.
He leaves behind a temporary vacuum of power.
Rex Tillerson, who spent his entire career at oil and gas giant ExxonMobil and rose to chairman and chief executive officer, has been nominated to succeed Kerry, but has not yet been confirmed by the Senate.
Holes to fill
Overall, out of 690 positions requiring Senate confirmation tracked by the Washington Post and Partnership for Public Service, President-elect Donald Trump has named only 28 people so far. There are thousands more positions the new administration needs to fill.
"We're ready to go at 12:01 tomorrow [Friday]," incoming White House press secretary Sean Spicer assured reporters on Thursday morning — little more than 24 hours before Trump is to take the oath of office.
The president-elect has asked two top key State Department officials to stay on a bit longer — Under Secretary Tom Shannon and Brett McGuirk, who was appointed by President Barack Obama as his special envoy for the global coalition to counter the so-called Islamic State group.
Shannon becomes acting secretary Friday afternoon.
"Certainly some policy agenda items will change," acknowledged State Department spokesman John Kirby on Thursday. "But the work [at U.S. embassies around the world] will go on."
Erin Walsh, a former senior adviser in the Bureau of Near Eastern Affairs who left government to become a Goldman Sachs executive, is to be the White House official in charge of filling all the vacancies at the State Department and the U.S. Agency for International Development.
WATCH: Spicer Praises Diversity in Trump Administration
Additionally, 536 "beach head" team members will descend on the State Department and other agencies for up to 120 days to assist those designated as secretaries.
"In some cases they stay on," according to Spicer, who said that all the Cabinet nominees have been selected. "You'll see a lot more activity at that lower level" to fill undersecretary, deputy secretary and ambassadorial posts.
No appointee below the secretary has been named for the State Department. The same is true for the departments of defense and treasury.
Concerns of vulnerability
Moments of transition are potential moments of vulnerability. “That's one reason why, normally, every effort is made to have a quick and clear changeover of senior officials, said Professor Erik Goldstein, a scholar of diplomacy at Boston University. "But it should be recalled that there remains in place a highly trained and experienced foreign service able to deal with all emergencies. The world is also now used to this four-to-eight-year cycle."
Others are more concerned.
"The State Department will be in real trouble. Tillerson knows little about diplomacy, and is not likely to be given the opportunity to bring in a really, really good veteran as deputy secretary," said Kentucky University Professor Emeritus John Stempel, a former director of the State Department's operations center.
He predicts the new president "will not take well to diplomatic niceties and ways of doing business — to his discredit and perhaps downfall."
Stempel told VOA that his friends and former colleagues in Washington predict a wholesale departure of senior career diplomats who will not tolerate Trump's "narcissistic ways, which are the opposite of diplomacy."
The concern extends to the other side of the Atlantic, according to Boston University's Goldstein, who told VOA that Trump's comments are "having shockwaves across Europe, especially those areas only liberated from Soviet control 25 years ago."
Trump has been criticized by both Republicans and Democrats for a soft stance toward Russia and its president, Vladimir Putin.
Goldstein, founder of the journal Diplomacy and Statecraft, acknowledged the possibility of significant diplomatic realignments in the near future because of Washington and the uncertainty created by Britain, the other stabilizer within the alliance, leaving the European Union. He expressed hope that "a clear signal from the new [Trump] administration could quickly restore that sense of equilibrium."