The European Union (EU) and NATO are united like never before. The US and its Western allies have imposed numerous financial and economic sanctions against Russia, including its removal from the SWIFT bank payments system.

We need to do more, starting with a ban on Russian oil. While cessation of Russian oil and gas purchases could drive prices higher and hurt the US economy, this danger is overestimated. A little more than a year ago, the US was the world’s largest oil and gas producer. Recent cutbacks on US production could be reversed.

Increased domestic oil and gas production, combined with continued sanctions, would not only harm the Russian economy, but they would also benefit the US. President Biden could achieve a successful double whammy — sanction Russia without hurting the US economy.

A no-fly zone also needs to be established. General Philip Breedlove, a former NATO Supreme Allied Commander, and other strategists, support securing Ukrainian airspace. Admittedly, this move presents dangers given that we are confronting a criminal dictator armed with nuclear weapons. Yet without such a measure, innocent men, women, and children of Ukraine will continue to be slaughtered. If Russia is not stopped now, another country and its people will soon become the next victims and the world will be held hostage to the same nuclear blackmail.

Precedents exist for NATO and NATO members to intervene in conflicts where alliance members were not involved, such as Syria and Bosnia. In April 1993, NATO enforced a no-fly zone over Bosnia and Herzegovina, at the request of the UN, to protect blue beret peacekeeping forces. No legal barrier prevents us from doing the same in Ukraine, a country that has sought NATO assistance and invited a no-fly zone to keep its population from being decimated.

Russian leader Vladimir Putin’s intent is evident. He wants to wipe Ukraine off the map. He has blocked civilian escape corridors from Mariupol, agreed to ceasefires, and then allows his forces to shell those trying to escape. The open question is whether the US and the EU can afford not to intervene? Military and humanitarian aid must be delivered to Ukraine. This can only be effected by ensuring Russian forces do not interfere.

The issue is not whether we stop Putin. It is when we stop him. The time is now. The US must have the same level of courage and resolve it displayed in the past when allies cried for help and our national interest was threatened. From Presidents Roosevelt and Truman during the Second World War to President Kennedy during the Cuban missile crisis to President Reagan during the Cold War, US leaders have made tough decisions and taken tough action.

Putin’s claims of liberating oppressed Russian people throughout European countries (like Hitler’s about protecting German people in various countries) is ludicrous. His argument that Ukrainians are fighting for freedom as a consequence of the “Stockholm syndrome“ induced by subjugation by the West is absurd. Yet his stated intent should not be discounted or ignored. He will follow through if not stopped.

Sanctions must be expanded to be all-encompassing and must continue even after Russia removes its troops from Ukraine. Relief should only be considered after Putin and his gang are no longer in control.

History reminds us of Neville Chamberlain’s comments to the British Parliament after Hitler’s march through Europe betrayed his promises and agreements: “Mr. Hitler did not live up to his word.” The world would have been a better place had Hitler been stopped sooner — millions of lives would have been saved.

Ukrainian President Volodymyr Zelenskyy and the people of Ukraine are fighting not just to keep Ukraine free, but for all of us. They are standing up for the principles of freedom, democracy, and human decency. The US and its European allies should do the same.

Adrian Zuckerman is a Romanian-born American lawyer and is currently Of Counsel to DLA Piper. He was the United States Ambassador to Romania from 2019 to 2021, when Romania signed a 10-year defense cooperation agreement with the U.S. In January 2021, President Iohannis awarded him with Romania’s highest civilian award, the Star of Romania, Order of the Grand Cross.