John McCain, John Barrasso, John Hoeven and Ron Johnson, all Republicans, represent Arizona, Wyoming, North Dakota and Wisconsin, respectively, in the Senate.

We recently visited Norway, Estonia, Latvia, Lithuania and Moldova. In each country, our allies want a stronger immediate response to Russia’s annexation of Crimea and its ongoing subversion of Ukraine. They also believe, as we do, that Russian President Vladimir Putin’s latest acts of aggression require an enduring strategic response from the United States, Europe and NATO. It should be clear to all that Putin’s Russia has taken a dark turn. There is no resetting this relationship. We cannot return to business as usual.

Western countries had high hopes for our relationships with Russia after the Cold War and acted on that basis. We provided billions of dollars to help Russia’s transition from communism. We created new mechanisms for consultation. We expanded trade. NATO committed not to deploy significant military capabilities onto the territory of new alliance allies, even as it expanded. In short, the West sought to include Russia in the promise of a Europe whole, free and at peace — a vision we still believe would benefit all participants.

Unfortunately, hope of a constructive relationship with Russia under Putin has vanished. A friendly rival has become, at best, an unfriendly adversary. Putin will not compromise his quest to dominate Russia’s sovereign neighbors (not least as a cynical way to build support at home for his corrupt and autocratic rule). He may play along with Western diplomats eager to avoid conflict, as happened recently in Geneva, but only as a way to consolidate his gains, divide the United States and Europe, play for time and prepare to push further. Western weakness emboldens Putin. The only thing he respects, and that can change his calculus, is greater strength.

We must make policy on this basis. In the short term, the United States must expand sanctions to major Russian banks, energy companies and other sectors of Russia’s economy — such as the arms industry — that serve as instruments of Putin’s foreign policy. We should also expose the most egregious corruption of Russian officials and cut off those people, their business associates and relatives from Western economies and travel. Some of our European allies may hope to avoid tough sanctions, but weak measures will not stop Putin, and the costs of doing so will only grow with time.

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Ultimately, Putin’s actions in Ukraine require a strategic response. This does not mean a new Cold War. But it does require recognizing Putin’s geopolitical challenge to the post-Cold War order in Europe and preparing for a more competitive relationship with Russia.

NATO must recommit to its core missions of deterrence and collective defense. This requires a rebalancing of the alliance’s force posture and presence. NATO military capabilities must be increased and more evenly distributed across the alliance, including a more robust and persistent presence in Central Europe and the Baltic countries. Some steps in this direction are underway; these actions must be sustainable and enduring.

For NATO to do more for its members, its members have to do more for themselves and the alliance. The United States must reverse harmful cuts to its defense budget. And NATO allies must meet their commitment to spend at least 2 percent of GDP on defense as soon as possible.

We also need a transatlantic energy strategy. Europe remains dependent on Russian oil and gas, while U.S. supplies are growing faster than our ability to bring them to market (indeed, about $1.5 million worth of gas has to be “flared” — that is, burned uselessly because there is not enough capacity to transport or refine it — each day in North Dakota alone). It will take years to align European demand and U.S. supply, but we must start now. European countries must invest in the infrastructure to receive liquefied natural gas from the United States, as Lithuania is doing, and transmit it across Europe. For our part, the Obama administration should lift holds on terminal applications for liquefied natural gas and ensure their expeditious processing so the private sector can build new capacity for transport and storage. These actions could weaken Putin, support our allies, strengthen the U.S. economy, increase federal revenue and create thousands of good jobs.

Another fact repeatedly highlighted during our trip is that Putin is winning the war of ideas among Russian-speaking peoples in the former Soviet Union. Putin’s propaganda rests on lies, but it is effective and hardly refuted. We have all but given up on communicating the truth, in Russian, to Europe’s Russian-speaking populations. This needs to change, and the old state-run public diplomacy is not necessarily the answer. The private sector can play an important role.

Finally, the West must provide far greater diplomatic, economic and military support to Ukraine, Moldova, Georgia and other European countries that aspire to be part of our transatlantic community. We must show all of these countries that, as long as they meet the rightfully high standards for membership, the doors to NATO and the European Union remain open and the fundamental choices about their future foreign policy are for them to make — no one else.

The United States and Europe did not seek, or deserve, this challenge from Putin’s Russia. But we must rise to it all the same. Our shared interests and values depend on our resolve.