MOSCOW — Russia launched a fleet of bombers bound for Syria Tuesday from an Iranian air base, becoming the first foreign military to operate from Iran’s soil since at least World War II.

Besides enabling Moscow to bring more firepower to the Syrian conflict, analysts said, the new arrangement would expand Moscow’s political influence in the Middle East and speed the growing convergence between Moscow and Tehran.

From the air base, in Hamadan, northwest Iran, the Russian bombers destroyed ammunition dumps and a variety of targets linked to the Islamic State and other groups that had been used to support militants battling in Aleppo, the Russian Defense Ministry said in a statement.

Historians and US officials said the Iranian decision to let Russia base its planes and operations in Iran — even temporarily — was a historic one.

“This didn’t even happen under the shah,’’ said John Limbert, a former US foreign officer stationed in Iran, referring to the reign of Shah Mohammad Reza Pahlavi from 1941 to 1979. In the shah’s era, US military advisers moved in and out of Iran and a series of listening posts in the country’s northeast allowed US intelligence agencies to monitor the Soviet Union.

But the sense of sovereignty runs so deep in Iranian culture that US efforts to have a bigger presence in such a strategic location were repeatedly rebuffed. Limbert speculated that Russia is paying handsomely for the privilege and noted that for Iran today, the prospect of gaining revenue “can create a lot of flexibility.’’

The bombers — too big for the air base Russia established in Syria last September — had been flying missions from Russia, a trip that is 1,000 miles longer, officials said. The main difference is that the planes will be able to carry heavier payloads, adding new muscle to the recently faltering Syrian effort in Aleppo.

Observers in Aleppo described a particularly heavy day of bombing there, even if they could not identify the bombers, with civilians bearing the brunt of the strikes. “The bombing today was intensive and massive,’’ said Mohamed al-Ahmed, a radiologist in an Aleppo hospital reached via Viber, who said he had counted 28 victims so far.

Beyond any tactical advantages on the battlefield, launching Russian bombers from Iranian territory also seemed to be part of a grander plan by President Vladimir Putin to cobble together a coalition to fight in Syria with Russia at its center. The use of the Iranian base follows Putin’s recent détente with Turkey and amid Russian-American talks on cooperating more in the fight against the Islamic State in Syria.

“I think what Russia is trying to do is put together a broader coalition that goes beyond Russian-Iranian cooperation,’’ said Andrey Kortunov, director general of the Russian International Affairs Council. “They consider this operation as another bargaining chip in their negotiations with the West.’’

Russia’s expanded presence has greatly limited US options.

Now, any operation would have to be coordinated with Russia to avoid conflicts over airspace, and so far the Pentagon has been highly suspicious of such coordination. An effort by Secretary of State John Kerry to work out some kind of cooperation — both to fight the Islamic State and to provide humanitarian access to besieged cities — has largely failed.

On Monday, Sergei Shoigu, the Russian defense minister, said that Moscow and Washington were coming closer to an agreement on Syria that would let the two sides fight together. Moscow has felt pressure to reach a political settlement as the humanitarian situation has deteriorated in Aleppo and Syrian government forces have suffered a series of setbacks there and in Latakia.

The arrangement seems to have brought Tehran and Moscow into greater agreement on Syrian President Bashar Assad, who has never enjoyed absolute support from Russia. “The Iranians have been all in on Assad, and I think the Russians have now moved in that direction,’’ said Cliff Kupchan, a specialist on Russia and Iran at the Eurasia Group, a political analysis firm in Washington.

The new flights help solidify Russia’s presence in the Middle East.

Russia “now views Iran as a powerful ally in the region and a stable source of income for its state industries,’’ said Konstantin von Eggert, a political analyst on Dozhd, a Russian independent television channel. “Tehran is a rich anti-American regime in a strategic region important to US interests. What could be better for Putin?’’