BERLIN-Germany's fast-paced rearmament is causing growing concern in Europe, rekindling a century-old debate about how much hard power Berlin should have.

The unease is becoming more acute as the Alternative for Germany tops opinion polls. The far-right party, known as the AfD, has embraced Moscow and wants to end what it calls Germany's "culture of guilt" around its Nazi-era crimes.

"We remember all too well where a rearmed Germany in the hands of a far-right, pro-Russian party can lead," Poland's Foreign Minister Radoslaw Sikorski, one of the few Polish officials who has long supported a stronger German military, told a German newspaper last week.

Days earlier, Jean-Luc Mélenchon, the far-left politician currently polling second among candidates in France's 2027 presidential election, said: "They want to build the largest conventional army in Europe. If I were president, I would tell them that I don't think that is a good idea."

Just a few years ago, Germany was widely seen as free-riding on the defense budgets of its U.S., French and British allies. President Trump led a chorus of Western leaders pressing Berlin to match military spending with its economic heft. Chancellor Friedrich Merz has since earmarked more than half a trillion dollars for the armed forces over the next decade.

Yet some European officials are now beginning to worry that the buildup is shifting the balance of power on the continent. Some fear that even without the AfD, a rearmed Germany and Russia will emerge as the continent's two biggest powers and Berlin might eventually shift back to accommodating the Kremlin to avoid conflict.

Sharpening concerns, Germany's military procurement has so far benefited mainly German arms-makers. Officials here say they are sensitive to their neighbors' worries but this has yet to translate into a new approach.

This is reminiscent of what historians call "the German question," a debate among European powers in the 19th century about how powerful a unified Germany could become before it posed a threat to peace. After Germany started two world wars, the answer came: Not too much.

Post-World War II Germany was locked into a U.S.-led North Atlantic Treaty Organization. When the Cold War ended, a reunified Germany focused on making money and avoiding military entanglements.

Russia's full-scale invasion of Ukraine changed that, kick-starting the biggest rearmament effort on the continent since the the fall of the Berlin Wall. Last year alone, the German government procured defense contracts worth over three times as much as those in the U.K., according to the Kiel Institute for the World Economy, an independent think tank.

"This is a revolution and it will definitely have an impact on Germany's neighbors, the EU and trans-Atlantic relationship," said Lukasz Jasinski, an expert on German-Polish relations at the Polish Institute for International Affairs, a think tank based in Warsaw. "Germany is crucial for European security but it cannot become too big for Europe."

Populists have been particularly strident in articulating these fears. Karol Nawrocki, Poland's nationalist president, said in a speech this month that Germany didn't need Hitler to be anti-Polish.

The plaudits that greeted Germany's rearmament drive in 2022 led Berlin to believe it had free rein, said Liana Fix, senior fellow for Europe at the Council on Foreign Relations in Washington.

"My perception sometimes was that they had drunk too much of their own Kool-Aid," she said.

Her article "Europe's Next Hegemon: The Perils of German Power," which appeared in April in Foreign Affairs, punctured that bubble. The text caught the attention of Merz, who met Fix in Washington earlier this year, according to a German official.

The AfD's electoral victory this month in eastern Germany, where it scored its best result ever, sent another jolt. The party wants Germany to leave the European Union, lift sanctions on Moscow and resume Russian energy purchases. Some of its leaders have questioned NATO's utility.

There has been concern in Poland that a far-right German government would revive old territorial claims against its neighbor. After World War II, Germany lost large chunks of territory that once stretched as far east as Kaliningrad, now part of Russia. More than 12 million Germans were expelled from Eastern Europe.

Germany formally renounced these lands upon reunification in 1990, but some AfD leaders have tapped into the loss felt by some expellees. In 2023, AfD Chairwoman Alice Weidel referred to eastern Germany as "Mitteldeutschland," or central Germany, which some Polish politicians saw as veiled irredentism. Last year, her co-chair, Tino Chrupalla said, "I don't see any danger to Germany from Russia," adding that Poland might be a threat.

Past chancellors worked hard to keep allies on board. When Helmut Kohl pushed for France and the U.K. to bless reunification, he offered to limit the country's military.

This changed over time. After the eurozone crisis broke out, Angela Merkel imposed German-style fiscal discipline on debt-ridden Greece in exchange for a bailout. When Russia annexed Crimea, she ignored Ukrainian and Polish warnings against opening a second Nord Stream natural gas pipeline linking Germany directly to Russia.

Fix said Germany could address the misgivings by binding its rearmament closer to Europe. This could include joint European procurement, more coordination and integration of the defense industry, as well as joint command structures within NATO. It could also agree to a longstanding demand from cash-strapped allies for joint EU-level borrowing to fund defense.

Instead, Berlin recently exited multibillion-euro projects with France and the Netherlands. Almost two-thirds of 2025 military spending went to German companies, some 30% went into German production of mainly U.S. systems and close to 10% went outside Europe, according to the Kiel Institute. A tiny amount went to European allies.

The concerns about Germany's buildup are sharpening at a time when the U.S. is planning to downgrade its presence on the continent. Washington often played mediator between European countries with divergent interests and historical grievances.

Rym Momtaz, a researcher at Carnegie Europe, said France was concerned about Germany replacing it as a leading military-industrial power. Paris, she added, also believed that Berlin didn't understand that acting at scale across Europe was the only way to deter attacks on the region.

"I think there is widespread nervousness across the French system whether it is political, diplomatic or military about the role that Germany seems to want to give itself," she said.

In a recent cable seen by The Wall Street Journal, a European diplomat wrote that too often since the start of the war in Ukraine, Berlin was seeing what was good for Germany as necessarily good for Europe. Germany's allies needed to press Berlin to work with them.

Camille Grand, a former assistant secretary-general of NATO, said that some complaints were exaggerated. Germany was engaged in a necessary catch-up, he said, noting that it would have spent an additional $400 billion on defense since 1990 if it had met NATO's spending target of 2% of economic output.

"Germany wants to claim leadership; it isn't always making great efforts in keeping its partners happy," he added.

Diplomats and analysts doubt that Merz, the most unpopular chancellor in living memory, has enough political capital left to change course. Granting concessions to European neighbors in an effort to make Germany's rearmament more acceptable to them could even bolster Merz's nationalist opponents.

Wolfgang Ischinger, chairman of the Munich Security Conference and a former diplomat, said rearmament was always going to evoke fears given Germany's 20th century history. Germany, he added, should reassure its allies that it was aimed solely at meeting NATO and European commitments.

"It is not about making Germany great again."