On Sept. 18, President Vladimir Putin watched as the Russian military battled an imaginary Western invasion. (David Filipov,Joyce Lee/The Washington Post)

— The vast Russian military exercises that ended last week showed off a muscular fighting force practicing state-on-state warfare, NATO’s deputy military commander said, in one of the first assessments of a large-scale operation that put Russia’s neighbors on nervous alert.

The Zapad exercise, which rehearsed a conflict along Russia’s western borders, showed off a force that was marshaling itself “probably more quickly, more efficiently, with this underlying message that if you thought we were in decay, we’re not,” NATO’s Deputy Supreme Allied Commander Europe, British Gen. James Everard, said in an interview.

The exercise, whose active phase ended Wednesday, is an ­every-four-years effort that was held this month for the first time since Russia in 2014 annexed Crimea from Ukraine, then sparked war in the eastern part of Ukraine. Because Russia used exercises as cover ahead of both its operations in Ukraine and its 2008 invasion of Georgia, its neighbors were cautious this time as the Kremlin fired up its military machine.

Now Western allies are sifting through intelligence reports and starting the arduous work of assessing the capabilities of Russia’s military, which is deep into a reform that has translated the force from a neglected and struggling group into one that for two years has been able to project power into Syria, far from Russia’s borders.

Servicemen take part in the joint Russian-Belarusian military exercises Zapad-2017 (West-2017) at a training ground near the town of Borisov on September 20. (Sergei Gapon/AFP/Getty Images)

Everard said that the first formal assessments would likely not be ready before the end of October. But he said that some of the basics of effective large-scale warfare — an ability to pick up and move large numbers of troops, and then command them effectively — were on clear display.

“You see a recognition in the Russian hierarchy that if you are going to have a foundation of military force behind your stratagem, and I think they do, then it needs to work,” Everard said.

Military analysts also said the exercise was a chance for the Kremlin to shoot a message straight to the Pentagon and its allies that Russia has a formidable fighting force capable of mobilizing across its enormous territory — and it needs to be reckoned with.

But if the exercises showed off a Russian military that is much better trained and equipped than at any point since the Soviet collapse, the scenario of the exercises — an enemy from the West trying to overthrow the government in Moscow’s ally, Belarus, and being beaten back — also may reveal Russia’s greatest handicap.

Moscow says it is convinced it is under threat of assault by a hostile force in the West that is determined to bring its military to Russia’s borders. This, as President Vladimir Putin sees it, has already been done in the Baltics. He also believes the United States and NATO were the instigators of street protests that forced Ukraine’s president to flee to Russia in 2014. 

Viewed from that perspective, Zapad was intended to reinforce a point Putin made in December: That Russia is “stronger than any aggressor.”

Vladimir Frolov, an independent foreign policy analyst based in Moscow, said: “Russia is acting on a faulty threat assessment and seeks to fashion a military response to largely imaginary threats and challenges that are not military in nature. It’s all about strategic messaging of coercion and compellence directed at the U.S. and NATO, to prevent things the West has no intention of doing or the capability to accomplish.”

NATO says it is a defensive alliance and represent no military threat to Russia. Many NATO officials disbelieve the Kremlin’s stated concerns, saying they are an excuse to practice for war against the West.

Although Russia publicly declared that the exercises were small enough to exempt them from international transparency obligations, most Western observers said that the concurrence of drills and joint exercises across Russia’s vast territory made them far larger than what was formally announced. The Russian and Chinese navies drilled in the east. The Russian military exercised in Central Asia. Bomber flights ranged over the Norwegian Sea. Paratroopers were active far above the Arctic Circle.

Adding a nuclear edge to the war gaming, Russia carried out two tests of its new intercontinental ballistic missile, the RS-24, the first two days before Zapad began and the second on the culminating day of the exercise.

Western officials are still trying to estimate how many troops took part in the exercises. Some security officials and analysts ventured initial guesses that Zapad may have been a smaller exercise than other major efforts in recent years, although they said it was still a significant event.

“It was effectively a national-level military operation,” said Igor Sutyagin, a senior research fellow for Russian studies at the Royal United Services Institute, a London-based security think tank. He said his initial estimate was that between 65,000 and 72,000 troops took part.

Putin viewed a mock battle involving tanks, missiles, air power and paratroopers at a firing range in Luga, in northwestern Russia, and also watched a broadcast of Russia’s new Iskander-M missile being launched from a firing range in southern Russia to a target in Kazakhstan about 300 miles away. The weapons were not only a fearsome show of Russian firepower but also a sparkling advertisement for the nation’s arms exporters.

“The president was very positive about the conduct and the result of that event,” Putin’s spokesman, Dmitry Peskov, told reporters Friday.

As the exercise unfolded, the Pentagon stepped up the presence of U.S. forces in the region. The U.S.-led heavy armored battalion deployed to Poland was in the process of rotating, meaning it was temporarily doubled. The U.S. Air Force sent three extra F-15 fighter jets to patrol the skies over the Baltics. And nearly 500 U.S. Army troops fanned across the Baltics for the month of September to do exercises.

“We train hard to have a combat edge, and that has a deterrent effect,” said Lt. Col. Hugh Jones, commander of the Germany-based U.S. Army squadron doing the troop exercises in the Baltics.

Some of the Russian military capabilities seen by NATO leaders confirmed their preexisting concerns.

“In 24 to 48 hours, some parts of the Russian armed forces could be ready to invade one Baltic state or all of them,” Lithuanian Defense Minister Raimundas Karoblis said in an interview. “It’s clear that it’s not only defense, but it’s also about offense.”

Part of the exercise rehearsed cutting off the Baltic states of Estonia, Latvia and Lithuania from the rest of NATO, Latvian Defense Minister Raimonds Bergmanis told Latvia’s LETA news agency. That is a nightmare scenario for the alliance because Russia has stationed powerful antiaircraft missile systems in its exclave of Kaliningrad, creating challenges for any Western attempt to retake the region.

Despite the Western worries, the training may not have been flawless.

“What had been expected but did not happen was the demonstration of readiness of the newly formed divisions, which adds credibility to the proposition . . . that they are rather far from being combat-capable,” said Pavel Baev, who studies the Russian military at the Peace Research Institute Oslo.

Other embarrassing incidents included a Tu-22M long-range bomber overshooting a runway and a misfiring rocket from a Ka-52 attack helicopter that hit spectators.

The “Russian Air Force is feeling the pressure of the protracted deployment in Syria,” Baev said. “Typically, maintenance is the weakest link, and accidents multiply,” he said.

Still, during the exercise, top military and security officials held daily briefings to prepare for the worst-case scenario of an invasion, even as they said they thought it was unlikely one would occur.

“As a human being, when you see such events close to your country, you always think, ‘What if?’ ” said Lithuanian Col. Mindaugas Steponavicius, the commander of the Iron Wolf Brigade, Lithuania’s core fighting force.

Earlier this year, NATO deployed battalions of about 1,000 troops to each Baltic nation and Poland, a step that alliance leaders hoped would ease the risk that Russia would try to seize any territory from those nations.

“We all hoped that the Cold War or something comparable would never happen again,” said German Lt. Col. Thorsten Gensler, the commander of the German-led, multinational NATO battalion that has deployed to Lithuania to dissuade Russia from attacking NATO territory. “So it is a kind of deja vu for me to be here.”

Filipov reported from Luga, Russia.