“Russian President Vladimir Putin ordered the deployment of troops to two breakaway regions in eastern Ukraine after recognising them as independent on Monday… [earlier that day] in a lengthy televised address packed with grievances against the West, a visibly angry Putin said eastern Ukraine was ancient Russian land… Putin's announcement drew international condemnation and immediate U.S. sanctions to halt U.S. business activity in the breakaway regions and ban import of all goods from those areas.” Reuters

Both sides fear that war is imminent:

“Putin left no room for negotiation with the Biden administration… Literally within minutes of completing his television address, Putin sent ‘peacekeepers’ into eastern Ukraine. His likely next move will be to stage some sort of incident in which he claims (as he did in Georgia in his war there) that the Ukrainians are the aggressors, and that Russia is acting only in defense of ethnic Russians…

“That ‘defense’ could lead right into the streets of Kyiv. Putin demanded in his address, as he has before, that Ukraine ‘cease hostilities’ in these areas—in other words, that the legitimate government of Ukraine stop trying to control its own territory—and he warned that ‘all responsibility for the possible continuation of the bloodshed will be entirely on the conscience of the regime ruling on the territory of Ukraine.’ This is the pretext for war.”
Tom Nichols, The Atlantic

“While the United States talks of off-ramps, de-escalation and the path of diplomacy, Putin is prosecuting a multifaceted war against the West. He announced his hostility at the Munich Security Conference in 2007 and opened the conflict with a major cyberattack against Estonia later that year. After the subsequent invasion of Georgia, annexation of Crimea, conflict in Donbass, intervention in Syria, blockade of Ukraine, hybrid attacks across the West, including the use of chemical weapons in assassination operations in the United Kingdom, and now recognition of Donetsk and Luhansk, it is beyond time for the West to abandon hopes for partnership…

“During Monday’s meeting of the Security Council of Russia, its deputy chairman, former President Dmitry Medvedev, observed that Russia’s invasion of Georgia, which also included the recognition of two provinces, led to no firm response from the West. The lesson, he concluded, is that the West will once again stand by, since ‘Russia is more important than Ukraine.’ It’s time for the Biden administration to prove otherwise.”
Peter Rough, New York Post

“Let’s assume for a moment that Vladimir Putin succeeds in gaining full control of Ukraine, as he shows every intention of doing… The most immediate threat will be to the Baltic states. Russia already borders Estonia and Latvia directly and touches Lithuania through Belarus and through its outpost in Kaliningrad. Even before the invasion, some questioned whether NATO could actually defend its Baltic members from a Russian attack. Once Russia has completed its conquest of Ukraine, that question will acquire new urgency…

“This takes place, moreover, as China threatens to upend the strategic balance in East Asia, perhaps with an attack of some kind against Taiwan… These simultaneous strategic challenges in two distant theaters are reminiscent of the 1930s, when Germany and Japan sought to overturn the existing order in their respective regions. They were never true allies, did not trust each other and did not directly coordinate their strategies. Nevertheless, each benefited from the other’s actions…

“It is time to start imagining a world where Russia effectively controls much of Eastern Europe and China controls much of East Asia and the Western Pacific. Americans and their democratic allies in Europe and Asia will have to decide, again, whether that world is tolerable.”
Robert Kagan, Washington Post

“NATO must be prepared to recognize the new reality of a more adversarial Russia. This will require new force deployments, logistics and emergency procedures, and deepening cooperation in the nonmilitary spheres. Temporary, rotating deployments of NATO forces to the Baltic states are being increased now. Because the Baltics are the likely next targets, NATO must move to make such forward stationing permanent…

“During the Cold War, NATO built and operated a complex pipeline system to provide fuel to its forces. In a similar vein, NATO could today commence planning for an allied public-private partnership to construct additional gasification facilities in America and Canada, and regasification terminals in Europe, which could eliminate European dependence on Russian gas. This could be an important component of an allied infrastructure program to free Europe from Russian coercion, stimulate European economic development and at the same time provide the means to reduce the carbon footprint from the coal-burning power plants in Europe.”
Wesley K. Clark, USA Today

Other opinions below.