The strikes have involved aircraft never before tested in combat, including the Sukhoi Su-34 strike fighter, which NATO calls the Fullback, and a ship-based cruise missile fired more than 900 miles from the Caspian Sea, which, according to some analysts, surpasses the American equivalent in technological capability.

Russia’s jets have struck in support of Syrian ground troops advancing from areas under the control of the Syrian government, and might soon back an Iranian-led offensive that appeared to be forming in the northern province of Aleppo on Wednesday. That coordination reflects what American officials described as months of meticulous planning behind Russia’s first military campaign outside former Soviet borders since the dissolution of the Soviet Union.

Taken together, the operations reflect what officials and analysts described as a little-noticed — and still incomplete — modernization that has been underway in Russia for several years, despite strains on the country’s budget. And that, as with Russia’s intervention in neighboring Ukraine, has raised alarms in the West.

In a report this month for the European Council on Foreign Relations, Gustav Gressel argued that Mr. Putin had overseen the most rapid transformation of the country’s armed forces since the 1930s. “Russia is now a military power that could overwhelm any of its neighbors, if they were isolated from Western support,” wrote Mr. Gressel, a former officer of the Austrian military.