President Putin, in marking the 80th anniversary of the Soviets’ World War II victory over Nazi German forces in the battle of Stalingrad, on Thursday invoked the long and grueling fight as justification for the conflict in Ukraine.

Mr. Putin laid a wreath at the eternal flame of the memorial complex to the fallen Red Army soldiers at Volgograd, the current name of the city, which stretches along the western bank of the Volga River. The  Mamayev Kurgan hillside is where some of the fiercest fighting took place, and the memorial is dominated by a 279-foot sculpture of a sword-wielding woman, “The Motherland Calls,” Europe’s tallest statue.

After the wreath-laying, he said: “Now, regrettably, we see that the ideology of Nazism, in its modern guise, in its modern manifestation, once again poses direct threats to the security of our country. Again and again we are forced to repulse the aggression of the collective West.”

Mr. Putin and other Russian officials frequently characterize Ukraine as a hotbed of neo-Nazi beliefs, though the Ukrainian president, Volodymyr Zelensky, is of Jewish descent.

Referring to Germany’s recent decision to supply advanced Leopard battle tanks to Ukraine, Mr. Putin warned that “a modern war with Russia will be quite different for them.”

“It’s incredible, but it’s a fact: they are threatening us again with German Leopard tanks with crosses painted on their armor,” Mr. Putin said.

“And they are again going to fight Russia on the territory of Ukraine with the hands of Hitler’s followers, the Banderites,” he said, referring to a World War II-era Ukrainian nationalist leader, Stepan Bandera, who was widely considered to be a Nazi collaborator.

The Russian strongman issued a veiled threat to use a broader range of weapons in Ukraine, though he did not mention nuclear weapons specifically. “Those who expect to win on the battlefield apparently do not understand that a modern war with Russia will be utterly different for them. We are not the ones sending our tanks to their borders,” Mr. Putin said, in a reference to the military assistance promised to Ukraine by its European and American allies. “But we have a way to respond,” he added, “and it will not just end with the use of armored vehicles.”

The battle of Stalingrad resonates deeply in Russia.

The five-month fighting between August 1942 and February 1943 is regarded as the bloodiest battle in history, with the death toll for soldiers and civilians reaching as high as 2 million. Most of the city was reduced to rubble before Nazi forces surrendered on February 2, 1943.

It was a major turning point in the European theater of World War II, and the battle remains an immense source of pride in modern Russia, lauded as a demonstration of military might and moral seriousness.

The city was renamed in 1961 as part of the Soviet Union’s rejection of dictator Joseph Stalin’s personality cult. Calls for the restoration of its old name haven’t received the Kremlin’s blessing, but the Moscow Times reported that in recent years that the city has reverted to the name Stalingrad on major holidays and anniversaries. On Wednesday, a new monument to Stalin was unveiled in the city.

As Russian forces struggle to gain ground in Ukraine, lawmakers from the dominant United Russia party have been told to liken the Ukraine fight to Stalingrad, the newspaper Kommersant reported.

Some Russians on Thursday made the connection explicit. “The achievement of our fathers and grandfathers, showing unprecedented heroism, valor and self-sacrifice during the defense of Stalingrad, still inspires our courageous soldiers who carry out responsible combat missions on the fields of the special military operation and defend the sovereignty, independence and security of our country,” the Russian Orthodox Church head, Patriarch Kirill, said, using the official characterization of the conflict that began nearly a year ago.

The Communist Party head, Gennady Zyuganov, after laying flowers at the Unknown Soldier memorial outside the Kremlin, said he hoped Russian forces would prevail in Ukraine.

“To do this, it is necessary to adopt the unique experience of the victorious Red Army, the Battle of Stalingrad, Oryol, Kursk,” Mr. Zyuganov said.