It’s less than six years since President Obama mocked presidential contender Mitt Romney for warning about the resurgent threat from Russia. In one of the most memorable lines of the 2012 election, Obama scoffed that “the 1980s are now calling to ask for their foreign policy back because, you know, the Cold War’s been over for 20 years.”

Today, there’s plenty of evidence that the Cold War was already on its way back, with a vengeance. Russia’s President Vladimir Putin seized every opening presented by Obama’s policies of “reset,” “flexibility,” appeasement and retreat. During Obama’s second term, Russia made its military reentry via Syria into the conflicts of the Middle East, shored up its ties to Iran, and began reconfiguring the borders of Eastern Europe and the rules of the post-Soviet world order by snatching Crimea from Ukraine. In Washington, American politics has been embroiled since the 2016 election in investigations and bitter quarrels involving allegations of Russian dirty tricks.

By now, the upshot is a global landscape of rising frictions and growing risks of military confrontation between Russia and the United States. For years, Putin’s strategy has been to test the limits of American tolerance — buttressing his projects with a massive military modernization and buildup, while daring the U.S. superpower to stop him. Obama

failed this challenge, bequeathing to President Trump the job of redrawing those vanished red lines, and restoring a credible U.S. strategy of deterrence.

That has become far more difficult and dangerous than it might have been a decade ago. As the director of the U.S. Defense Intelligence Agency testified to Congress just last week, “Although Russia repeatedly emphasizes that is it not interested in a new Cold War with the United States, it has also made clear that it will no longer reconcile with the West through concessions or a policy of appeasement.”

Recent weeks have brought a number of flashing red signals over where Russia is headed, from the Middle East, to the Baltics and beyond.

Most dramatic was Putin’s March 1 annual speech to the Russian parliament, in which Putin announced advances in Russia’s nuclear arsenal which he said have made it “invincible,” designed to defeat America’s missile defenses. Putin illustrated his speech (a la North Korea ) with video depictions of a next-generation Russian nuclear triad — land, air and submarine -based — including an animation of a missile striking the United States. Putin warned that Russia is done deferring to the West: “No one listened to us. Listen to us now.”

Analysts are debating whether Putin was exaggerating Russia’s nuclear prowess, showboating in the runup to Russia’s next presidential vote, scheduled for March 18. Putin, whose regime controls the Russian media and has a history of annihilating his opponents, is expected to win. Officially, that will add another six years to Putin’s long reign, which began with the resignation of President Boris Yeltsin, on Dec. 31, 1999.

Whatever the tweaks yet in store for Russia’s massive nuclear arsenal, there’s virtually no room for doubt about Russia’s growing threat to the Baltics — Lithuania, Latvia and Estonia — and by extension to the North Atlantic Treaty Organization (NATO), to which all three nations belong. NATO’s ultimate guarantor of security is U.S. military power — and political willpower.

Last week, the RAND Corporation released a report assessing that Russia’s military is now well positioned to overrun the Baltics in a surprise attack, before NATO could muster an effective response. In a summary of key findings, the report warns that while NATO ultimately has the resources to win a protracted war, Russia is positioned to “achieve a rapid fait accompliin the Baltic states followed by brinksmanship to freeze the conflict.”

The RAND report details an alarming scene in Europe, in which NATO’s forces since the end of the Cold War have dramatically declined, with NATO refocusing on “lighter forces” that can easily be deployed to places such as Afghanistan. By contrast, Russia since 2008 has been expanding and refining “its capability for high-intensity conventional warfare,” and has placed the highest density of its “most capable ground and air forces” near the Baltics.

Meantime, from Syria’s cauldron of warring factions, where both Russia and Iran have been fighting on the side of the Assad regime, there were reports last month that scores of Russian mercenaries had died in a failed attack on a post held by U.S. troops and their allies.

There were no reports of any U.S. casualties. But the bottom line, as summed up by veteran Russia correspondent Gregory White, in a Feb. 13 dispatch on Bloomberg News, is that “The war in Syria is now threatening to embroil the major powers in direct conflict.” White noted that “The raid was likely the first such deadly conflict between the former Cold War rivals since the Vietnam War, according to Russian experts.”

Plenty of murk surrounds the precise circumstances of this clash, which Defense Secretary James Mattis described in a press briefing last monthas “perplexing.” To attack the Americans, the Russians crossed the “deconfliction” line with which Russia and the U.S. have tried to avoid coming into direct conflict in Syria. On Feb. 22, the Washington Post reported that the Russian mercenaries likely acted with at least an indirect nod from the Kremlin.

On the broader world scene, Russia has been holding joint military exercises with China, abetting sanctions-busting smuggling by North Korea, and is suspected in the poisoning in Britain last week of a retired Russian double agent and his daughter.

It all adds up to an ever more menacing showdown, in which Trump has every reason to consult and adapt the 1980s Ronald Reagan playbook, including beefing up U.S. military power and defenses. It is becoming imperative that the U.S. stand up to Putin’s threats. Americans would be wise to understand that while this might play in some quarters as reckless war-mongering, it is vital to reestablishing deterrence.