Russia's use of an Iranian air base to bomb rebel targets across Syria for the first time this week has allowed Moscow to show off sophisticated weaponry as it seeks to cement ties with Tehran and expand its influence in the Middle East.
While the tactical effect was unclear, Russian President Vladimir Putin got the public relations bang he presumably sought when Moscow-issued photos of a sleek Tu-22 bomber dropping a string of bombs appeared on news sites around the globe.
The episode thus is similar to Russia's first launch of salvos of cruise missiles from warships and a submarine last fall, a dramatic attack that reportedly did limited damage to Syrian opposition forces but drew huge headlines.
For now, it's unclear whether the long-range bomber attacks — like the cruise missiles — were meant mostly as a show of force or are part of a new strategic boost for Syrian President Bashar Assad's forces in the multi-sided civil war.
On Thursday, U.S. officials said satellite imagery showed four Russian Su-34 fighter jets parked by the flight line at Nojeh air base in western Iran, a day after they had conducted airstrikes in Syria.
Long-range Tu-22 bombers had launched the new air offensive with bombing runs Tuesday from Nojeh before flying back to a Russian base. Under an agreement to "deconflict" flights over Syria, Russian authorities had notified the American military in advance, U.S. officials said.
The Iranian base, far closer to Syria than bases in Russia, allowed the aircraft to carry less fuel and more munitions as they struck rebel forces and positions in Aleppo, Dair Alzour and Idlib provinces, Russian and Iranian officials said.
At a minimum, the shift this week suggests growing cooperation between Moscow and Tehran after last year's international accord to block Iran from building nuclear weapons.
Russia already has lifted a long-standing ban on the sale of its powerful S-300 surface-to-air missile defense system to Tehran. Iranian officials have said major components of the system have been delivered.
The two nations already are the strongest backers of Assad in the five-year war against U.S.-backed militias, Arab-backed forces and Islamist militants.
Up until now, however, Russia's military has relied on tanks, armored vehicles and aircraft stationed in Syria, not in Iran. Moscow has both an air and a naval base in Syria, its only foothold in the Middle East.
Russia's use of the Iranian base shows the world that Moscow's influence is growing, especially in the Shiite-led nations of the Middle East, said James Stavridis, a former NATO supreme commander who is dean of the Fletcher School of Law and Diplomacy at Tufts University.
"While not of significant tactical impact, this move has high symbolic strategic content," he said.
"This move is a signal not only to the U.S. and NATO, but also to Saudi Arabia and the gulf states and other Sunni countries," he said. "Russia is here to stay."
By allowing foreign troops on its soil for the first time since the 1979 Islamic Revolution — and Russians for the first time since World War II — Iran may be seeking to show it can end its isolation with or without the United States, analysts said.
The move also may signal that Russia seeks to play a larger role in regional security, including in Iraq, said Dmitry Gorenburg, a Russian expert at CNA, a Washington think tank.
Still, the latest bombing may be mostly for show — and to test new weapons and tactics.
In November, for example, Moscow inexplicably sent two Tu-160 Blackjack strategic bombers on a 8,000-mile flight from northern Russia around the European continent to hit targets in Syria.
It also allows Russia to further expend stockpiles of Cold War-era gravity bombs as it upgrades to more modern satellite-guided weapons.
Mark Toner, a State Department spokesman, told reporters that it's still unclear whether Russia's use of the Iranian base was a "one off thing" or the start of a new campaign.
Using the base on a regular basis probably would require new construction of ammunition bunkers and facilities for Russian support troops.
Toner said U.S. officials are examining whether Russia’s use of the Iranian base is a violation of a United Nations Security Council resolution that bans the supply, sale and transfer of combat aircraft to Iran without prior U.N. approval.
Moscow and Tehran were quick to dispute any violation, arguing that the Russian aircraft were not used within Iran. Iran’s government also denied that it had given any basing rights to Russia.
“These aircraft are being used by Russia's air force with Iran's agreement as a part of an anti-terrorist operation at the request of Syria's leadership,” Russia’s foreign minister, Sergei Lavrov, said at a news conference in Moscow.
There are potential risks for Iran in cozying up to Russia.
With the lifting of economic sanctions on Iran thanks to the nuclear deal, and the return of billions of dollars from frozen accounts, moderate Iranian leaders had indicated they were eager to return to the international fold and pursue business deals with the West.
European countries, already wary of Putin’s use of the military to seize parts of Ukraine and to threaten parts of Eastern Europe, may be wary of embracing an Islamic Republic that is increasingly linked to Moscow.