BERLIN — Within hours of being sworn into office, Germany’s new defense minister will be expected to hold talks with the U.S. defense secretary. A day later, he will represent Germany’s armed forces at a meeting with European allies awaiting critical decisions on the war in Ukraine.

That would not be an easy first week for any new government official, let alone one familiar only with local politics, with no experience on the national or world stage.

But that is the stage on which Boris Pistorius will soon find himself.

Though Mr. Pistorius has won praise for his nine years running the interior ministry of Lower Saxony, he has no background in foreign affairs or global security. For Germany’s allies, the transition may be just as disconcerting.

Little is known of his views on the biggest questions of the day, from military spending on NATO to his vision on Germany’s future approach toward Russia.

“He’s being thrown into the deep end immediately — and we’re all watching in suspense to see how the waters suit him,” said Uwe Jun, a political scientist at the University of Trier who focuses on Chancellor Olaf Scholz’s Social Democrats, the senior party of Germany’s coalition government.

Mr. Jun called the chancellor’s decision to promote Mr. Pistorius, a longtime stalwart of the Social Democrats, to such a heady position a “complete surprise.”

The choice was not just unexpected but also risky for a chancellor who has declared that his country needs to fundamentally rethink its military stance.

“Zeitenwende” — “turning point” — is the term Mr. Scholz has used to describe his vision for upending decades of a German foreign policy that was pacifist and tentative. He underpinned it with a massive spending package of 100 billion euros (about $108 billion) to reboot Germany’s armed forces for an era of increasing instability in Europe.

“This is not just a change of a minister, this is a change in a key ministry,” said Claudia Major, a defense expert at the German Institute for International and Security Affairs. “If he chose the right person, if this person is able to make things move — that will decide Scholz’s success on Zeitenwende.

Days after Russia invaded Ukraine last February, the new German chancellor captured world attention by pledging to finally meet Germany’s commitments to NATO to spend 2 percent of its gross domestic product on defense, and to modernize its army. Yet since then, Mr. Scholz’s government has appeared to lag behind its European allies in supporting Ukraine, always delaying long enough that it is seen as being pushed by its allies into supplying new weapons.

And though that approach is widely acknowledged as one laid out by the chancellor, who has repeatedly insisted on not “going it alone,” the face of this seeming halfheartedness was often his departing defense minister, Christine Lambrecht.

Ms. Lambrecht resigned after months of criticism over her handling of the army’s modernization, which critics skewered as slow and uninterested. And her public messaging on Ukraine often seemed tone-deaf. Most memorable was her trumpeting of Germany’s offer of 5,000 helmets to Ukraine at the start of the war — when other European countries were beginning to send weapons.

The first big test for Mr. Pistorius is already here.

This week, pressure is ramping up for Germany to deliver its Leopard 2 tanks to Ukraine, or at least to allow other European countries to do so. Because the battle tanks are German-made, such a transfer requires Berlin’s approval, and expectations are growing that a decision could be made by the end of the week.

On Thursday, the same day Mr. Pistorius is to start his term as defense minister, his American counterpart, Lloyd J. Austin III, is expected for talks in Berlin. Then on Friday, members of the U.S.-led Ukraine Defense Contact Group will meet at Ramstein Air Base in Germany.

Anton Hofreiter, head of the European Union committee in the German Parliament and a staunch advocate of supplying more weapons to Ukraine, said the allies — particularly those keen to send Leopards, like Poland, Finland and Spain — were expecting a green light.

“There is the expectation that there are no more delays with the Leopard, that Germany actually take on a coordinating role as the manufacturing country,” Mr. Hofreiter said.

Thomas Kleine-Brockhoff, a foreign policy expert at the German Marshall Fund, a Berlin-based think tank, said the best outcome for the Ramstein meeting would be the creation of a “European Leopard consortium.”

“But the key here is Germany,” he said.

While Germany is in a position to approve Leopard exports from other European countries, it is unlikely to be able to furnish many of its Leopard 2 tanks itself.

Last weekend, Armin Papperger, the head of the German weapons maker Rheinmetall, said his company needed a year to refurbish the 22 used Leopard 2 tanks it has in stock. Krauss-Maffei Wegmann, the builder of the tank, reportedly has some used Leopard 2 tanks in stock, but it has not said how many it could deliver, or when.

In his first public statement after being appointed, Mr. Pistorius, 62, signaled his readiness to meet expectations.

“I want to make the German armed forces strong for the times that lay ahead of us,” he told journalists on Tuesday. “I understand the meaning of this task at such a moment.”

Mr. Pistorius has received a cautiously warm welcome from the other two parties in Mr. Scholz’s three-way governing coalition, the Greens and the liberal Free Democrats.

“Boris Pistorius has a serious interest in the troops and security policy and is considered open to good arguments,” said Sara Nanni, the security spokesperson for the Greens in Parliament.

But given how critical the moment is, other coalition figures say they will not go easy on the new minister.

“He will not be given a grace period in view of the dramatic international situation and the state of the Bundeswehr,” said Marie-Agnes Strack-Zimmermann, head of the defense committee in Parliament, referring to the armed forces.

Ms. Strack-Zimmermann, a member of the Free Democrats, told the German website T-Online, “We will work constructively with him and support him, provided that he exclusively represents the interests of the soldiers.”

The Christian Democrats, the leading opposition party, promised collaboration but did not hold back their skepticism about the appointment of an international affairs novice to the job.

“The chancellor shows he does not take his own Zeitenwende seriously,” said the deputy chairman of their parliamentary faction, Johann Wadephul. Writing on Twitter, he criticized Mr. Pistorius’s lack of experience and called him a “selection from the B Team.”

Though Mr. Pistorius may be quickly measured based on the outcome of the Ramstein meeting, it is a questionable yardstick: The decision on tank deliveries, security experts agree, has probably already been made in the chancellery, in coordination with Washington.

Mr. Scholz has long been seen as the main force behind decisions on military support to Ukraine — and the most hesitant one. It is possible, said Mr. Jun, the political scientist, that the chancellor chose Mr. Pistorius on the assumption that the new minister would loyally toe the chancellery’s line.

But that is not a given, as so little about the new minister’s views are known.

One of the few foreign policy stances dug up on Mr. Pistorius by German media on Tuesday was his push in 2018 for Germany to abandon sanctions on Russia, calling them economically painful for Germany and ineffective in pressuring Moscow over its annexation of Crimea.

That was the Social Democrats’ party line at that time. In contrast, Mr. Pistorius’s statements on Russia since the invasion of Ukraine last year have been sharply critical.

But there is room for uncertainty about where the new appointee stands, said Mr. Kleine-Brockhoff.

“We know his professional character traits, we know his experience, but we don’t know his views on any key issues of the day,” he said. “This set of open questions is an issue, in and of itself.”